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Q1. The chart shows the processes involved in the manufacture of nitric acid from ammonia.

(a) Complete the word equation for the reaction that takes place in the first reaction vessel.

ammonia + ...................................... nitrogen monoxide + water (1)

(b) What is the use of the platinum gauze in the reaction vessel?

..................................................................................................................................... (1)

(c) To convert nitrogen monoxide into nitric acid, two further reactants are needed. What are they?

................................................................ and ............................................................ (1)

(d) Complete the word equation below, to show how to make the fertiliser, ammonium nitrate.

................................ + ......................... ammonium nitrate + water (2)

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(e) Calculate the percentage of nitrogen in the fertiliser, ammonium nitrate NH4NO

3.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 7 marks)

##

Here is a symbol equation, with state symbols, for a chemical reaction between solutions of lead nitrate and potassium chloride.

Pb (NO3)

2 (aq)

+ 2 KCl (aq)

2KNO3 (aq)

+ PbCl2 (s)

The equation tells you the formulae of the two products of the reaction.

1 .................................................................................................................................

2 ................................................................................................................................. (2)

(b) What else does the equation tell you about these products?

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (2)

(Total 4 marks)

Q3. Here is a word equation for a chemical reaction.

copper oxide + sulphuric acid copper sulphate + water

Write down everything that the word equation tells you about the reaction.

...............................................................................................................................................

...............................................................................................................................................

............................................................................................................................................... (Total 4 marks)

(a) What are the names of the two products?

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Q4. When a solution of lead nitrate is added to a solution of sodium chloride, a white precipitate of lead chloride is produced.

(a) (i) Why is a precipitate formed?

...........................................................................................................................

........................................................................................................................... (1)

(ii) Complete and balance the equation for this precipitation reaction.

Pb+2

(aq) + Cl–

(aq) →

(3)

(b) Complete the table below by writing in the name and formula of the precipitate formed for each reaction. If there is no precipitate, write “no precipitate”.

(5)

(Total 9 marks)

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Q5. Sodium carbonate reacts with acids.

(i) Complete the word equation.

sodium carbonate + hydrochloric acid → sodium chloride + ...................... + water (1)

(ii) Name the salt produced if sodium carbonate reacts with dilute nitric acid.

........................................................................................................................... (1)

(Total 2 marks)

Q6. The diagrams show what happens when an acid is added to an alkali.

(a) What is present in the solution at stages 2 and 3 apart from universal indicator and water?

(i) At stage 2 .........................................................................................................

(ii) At stage 3.......................................................................................................... (3)

(b) Write an ionic equation to show how water is formed in this reaction and state the sources of the ions.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 6 marks)

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Q7. The diagrams show what happens when an acid is added to an alkali.

(a) What is present in the flask at stage 2, besides universal indicator and water?

..................................................................................................................................... (1)

(b) Write an ionic equation to show how water is formed in this reaction and state the sources of the ions.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 4 marks)

Q8. Read the passage carefully and then answer the questions.

From Chemistry Matters by Richard Hart, reproduced by permission of Oxford University Press

The electrolysis of acidified water

After a few drops of dilute sulphuric acid have been added to some distilled water, there will be three types of ion in solution:

from the water, H2O(l) → H+(aq) + OH–(aq)

from the acid, H2SO

4(aq) → 2H+(aq) + SO

4

2– (aq)

When the electrodes (anode and cathode) in a circuit are put into the acidified water, the hydroxide ions and the sulphate ions are both attracted to the electrode called the anode. However, it is harder for the sulphate ions to give up their electrons than for the hydroxide ions to do this. So the hydroxide ions are the ones which react and bubbles of oxygen are formed at the anode.

There are only hydrogen ions to be attracted towards the cathode and, when they get there, they take up electrons to form hydrogen molecules.

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Even in a small volume of water acidified with dilute sulphuric acid there will be billions of ions. Some will be anions and some will be cations.

(i) Name the ions in water acidified with dilute sulphuric acid.

..................................................................................................................................... (1)

(ii) Explain why only some of the ions are attracted to the anode.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(iii) Balance the equation for the reaction of hydroxide ions at the anode.

4OH– → H2O + O

2 + e–

(1) (Total 4 marks)

Q9. (a) Ammonium sulphate is made by the reaction:

2NH3(aq) + H

2SO

4(aq) →(NH

4)

2SO

4(aq)

(i) Complete the three answers in the table.

(3)

Question Answer

How many hydrogens are there in the formula of ammonium sulphate?

..............................................................

What is the name of the substance with the formula NH

3?

..............................................................

What is the name of the substance with the formula H

2SO

4?

..............................................................

(ii) What is the main use for ammonium sulphate?

........................................................................................................................... (1)

(iii) A similar reaction is used to make ammonium nitrate. What is the name of the acid which must be used?

........................................................................................................................... (1)

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(b) NH3 is made by the reversible reaction:

N2(g) + 3H

2(g) 2NH

3(g)

(i) Explain what the term reversible reaction means.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) What is the name of the raw material which is the source of nitrogen (N2)?

........................................................................................................................... (1)

(iii) Nitrogen is an element. Explain what the term element means.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 10 marks)

Q10. Ammonium nitrate and ammonium sulphate are used as fertilisers.

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(i) Which acid reacts with ammonia to form ammonium nitrate?

.................................................................................................................................... (1)

(ii) Which acid reacts with ammonia to form ammonium sulphate?

.................................................................................................................................... (1)

(iii) The reactions in (i) and (ii) are both exothermic. How can you tell that a reaction is exothermic?

....................................................................................................................................

.................................................................................................................................... (1)

(iv) The reactions in (i) and (ii) are both examples of acid + base reactions. What is the name of the chemical change which takes place in every acid + base reaction?

.................................................................................................................................... (1)

(Total 4 marks)

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Q11. The flow diagram shows how to make ammonia and nitric acid from the nitrogen in the air.

(a) A fertiliser is made by neutralising ammonia with nitric acid. What is the name of this fertiliser?

..................................................................................................................................... (1)

(b) In the flow diagram, why are two different catalysts used?

.....................................................................................................................................

..................................................................................................................................... (1)

(c) What happens to catalysts at the end of a reaction?

.....................................................................................................................................

..................................................................................................................................... (1)

(d) Explain why catalysts are used in many industrial chemical reactions.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

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(e) Explain, in terms of collisions between molecules, why a high pressure is used in the reaction between nitrogen and hydrogen.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 7 marks)

Q12. The flow diagram shows some stages in the manufacture of the fertiliser ammonium nitrate (NH

4NO

3).

(a) The elements needed to make ammonia (NH3) are obtained from natural gas and air.

Which element is obtained from the air?

..................................................................................................................................... (1)

(b) The word equation for the formation of nitrogen monoxide is:

ammonia + oxygen → nitrogen monoxide + water

The platinum catalyst needs to be heated only at the start of the reaction. Suggest why.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(c) Name the liquid A that reacts with nitrogen dioxide (NO2) to produce nitric acid (HNO

3).

..................................................................................................................................... (1)

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(d) Describe how ammonium nitrate (NH4NO

3) can be made from two of the products shown

in the flow diagram.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 5 marks)

Q13. (a) Magnesium burns in oxygen, forming magnesium oxide.

This equation represents the reaction.

Mg (s) + O2 (g) → MgO (s)

(i) Balance the equation. (1)

(ii) Give the meaning of the state symbols (s) and (g).

(s) ..............................................

(g) .............................................. (2)

(b) Use the Formulae of Some Common Ions table on the Data Sheet to help you to answer this question.

Magnesium also reacts with chlorine to form magnesium chloride.

Give the formula of magnesium chloride .................................................................. (1)

(Total 4 marks)

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Q14. Use the Formulae of Some Common Ions table on the Data Sheet to help you to answer this question.

Acids react with alkalis to form salts and water.

Complete the table below by writing in the name and formula of the salt formed in each reaction.

The first one has been done for you.

(Total 4 marks)

Acid Alkali Salt Formula of salt

Hydrochloric acid Sodium hydroxide Sodium chloride NaCl

Nitric acid Sodium hydroxide

Sulphuric acid Potassium hydroxide

Q15. This item appeared in the Wolverhampton Express and Star on October 31st, 1997. Read the passage and answer the questions that follow.

Fumes scare at factory

Workers were forced to flee a factory after a chemical alert. The building was evacuated when a toxic gas filled the factory. It happened when nitric acid spilled on to the floor and mixed with magnesium metal powder.

(a) The equation which represents the reaction between magnesium and nitric acid is:

Mg(s)

+ 4HNO3(aq)

→ Mg(NO3)

2(aq) + 2H

2O

(1) + 2NO

2(g)

Give the formula of the toxic gas that was produced.

.................................................................................................................................... (1)

(b) Explain, in terms of particles, how the toxic gas was able to fill the factory quickly.

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (2)

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(c) The reaction of nitric acid with magnesium metal powder is more dangerous than if the acid had fallen on to the same mass of magnesium bars. Explain why.

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (1)

(d) (i) Water was sprayed on to the magnesium and nitric acid to slow down the reaction. Explain, in terms of particles, why the reaction would slow down.

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(ii) Explain why it is better to add alkali, rather than just add water to the spillage.

..........................................................................................................................

.......................................................................................................................... (1)

(Total 7 marks)

Q16. (i) Which acid from the list should the student add to sodium hydroxide solution to make sodium sulphate?

ethanoic acid hydrochloric acid nitric acid sulphuric acid

..................................................................................................................................... (1)

(ii) When the acid was added to the alkali the beaker became warm. Name the type of reaction that releases heat.

..................................................................................................................................... (1)

(iii) Use the Data Sheet to help you to write the formula of sodium sulphate.

Formula: ..................................................................................................................... (1)

(Total 3 marks)

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Q17. Some drain cleaners contain a mixture of sodium hydroxide and powdered aluminium. When the mixture is poured into a drain it mixes with water and a chemical reaction takes place. The heat from the reaction helps to melt grease in the drain. Hydrogen gas is produced which stirs up the particles and helps to unclog the drain.

(a) Balance the equation for the reaction.

2Al(s)

+ ........ NaOH(aq)

+ ......... H2O → .........NaAl(OH)

4(aq) + 3H

2

(2)

(b) Why do the solid sodium hydroxide and aluminium powder not react when stored in a sealed container?

..................................................................................................................................... (1)

(c) Sodium hydroxide is a strong alkali and would react with any acids in the drain.

(i) Name the ion produced when any alkali is dissolved in water.

........................................................................................................................... (1)

(ii) Name the ion produced when any acid is dissolved in water.

........................................................................................................................... (1)

(iii) Name the compound formed when these ions react with each other.

........................................................................................................................... (1)

(Total 6 marks)

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Sando-K is a medicine. It is given to people whose bodies contain too little of a particular element.

Sando-K is a mixture of two compounds. The formulae of the two compounds are given below.

KHCO KC1

(a) Which metal do people given Sando-K need?

..................................................................................................................................... (1)

(b) Sando-K contains the ion, CO . Which gas would be produced if a dilute acid was added to Sando-K? (The Data Sheet may help you to answer this question.)

..................................................................................................................................... (1)

3

32–

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(c) The compounds in Sando-K contain ions.

Complete the two sentences below.

Atoms change into positive ions by ....................................... one or more

............................................................. .

Atoms change into negative ions by ......................................... one or

more .................................................... . (4)

(d) Electricity can be used to show that an aqueous solution of Sando-K contains ions.

(i) Draw a diagram of an apparatus that you could use to prove that Sando-K contains ions.

(4)

(ii) Explain, as fully as you can, what would happen when the electricity is switched on.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(Total 13 marks)

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Q19. Sodium carbonate is a useful chemical that can be made from sodium chloride.

(a) The flow chart below shows one way in which sodium carbonate can be made.

(i) Write the formula of sodium carbonate. Use the Data Sheet to help you to answer this question.

........................................................................................................................... (1)

(ii) 1. Give one example of a thermal decomposition reaction shown in the flow chart.

................................................................................................................

................................................................................................................ (1)

2. Explain what is meant by a thermal decomposition reaction.

................................................................................................................

................................................................................................................ (2)

(iii) Name one substance that is recycled in this process.

........................................................................................................................... (1)

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(b) When sodium carbonate solution is added to zinc sulphate solution a white solid is precipitated.

(i) Use the Data Sheet to help you to name the white solid that is produced in this reaction.

........................................................................................................................... (1)

(ii) State why this solid is formed.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(Total 7 marks)

Q20. (a) In an industrial process electricity is passed through a solution of sodium chloride in water. A student set up the apparatus shown below to investigate this process.

(i) Name gas X.

........................................................................................................................... (1)

(ii) Complete the half equation for the production of chlorine gas during the electrolysis.

............ Cl– → ............ e– → Cl2

(1)

(iii) The student found that the solution left in the cell was alkaline.

Which ion makes the solution alkaline?

........................................................................................................................... (1)

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(iv) Name the useful substance that can be obtained from the solution in the cell.

........................................................................................................................... (1)

(b) Sodium carbonate is another useful chemical that can be made from sodium chloride. The flow chart below shows one way in which sodium carbonate can be made.

(i) Write the formula of sodium carbonate. Use the Data Sheet to help you to answer this question.

........................................................................................................................... (1)

(ii) Salt is one raw material used in this process.

Name one other raw material used in this process.

........................................................................................................................... (1)

(iii) Sodium carbonate is one of the products of this process.

Name one other product.

........................................................................................................................... (1)

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(iv) 1. Give one example of a thermal decomposition reaction shown in the flow chart.

................................................................................................................

................................................................................................................ (1)

2. Explain what is meant by a thermal decomposition reaction.

................................................................................................................

................................................................................................................ (2)

(v) Name one substance that is recycled in this process.

........................................................................................................................... (1)

(c) When sodium carbonate solution is added to zinc sulphate solution a white solid is precipitated.

(i) Use the Data Sheet to help you to name the white solid that is produced in this reaction.

........................................................................................................................... (1)

(ii) State why this solid is formed.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(Total 13 marks)

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Q21. (a) This label has been taken from a packet of Andrews Antacid.

(i) Write the simplest ionic equation which represents a neutralisation reaction.

........................................................................................................................... (1)

(ii) Chewing the tablet cures indigestion faster than swallowing the tablet whole. Explain why.

...........................................................................................................................

........................................................................................................................... (1)

(iii) Write the formula of the magnesium compound present in Andrews Antacid. You may find the Data Sheet helpful.

........................................................................................................................... (1)

(b) The active ingredients in the Antacid react with hydrochloric acid in the stomach to give salts, water and carbon dioxide.

A student investigated how quickly the tablets react with excess hydrochloric acid.

40 cm³ of dilute hydrochloric acid were placed in a conical flask. The flask was placed on a direct reading balance. Two Antacid tablets were quickly added to the flask. The apparatus was weighed immediately. At the same time, a stop clock was started. The mass was recorded every half minute for 5 minutes.

The results are shown in the table below.

The main active ingredient in Andrews Antacid is calcium carbonate.

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(i) Balance the equation which represents the reaction between calcium carbonate and hydrochloric acid.

CaCO3(s)

+ .......... HCl(aq)

→ CaCl2(aq)

+ H2O

(l) + CO

2(g)

(1)

(ii) State the meaning of the symbol “(aq)”.

........................................................................................................................... (1)

(iii) Why does the mass of the flask and contents decrease?

........................................................................................................................... (1)

(c) (i) Plot the results on the graph below and draw a smooth curve to show how the mass of the flask and its contents changes with time. Label this curve “A”.

(3)

(ii) One of the results does not appear to fit the pattern. Circle this result on the graph. (1)

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(d) The student did a second experiment. The only change was that the acid was twice as concentrated.

On the graph, sketch a second curve to show a possible result for this experiment. Label this curve “B”.

(2) (Total 12 marks)

Q22. Limestone (CaCO3) is a raw material. On strong heating it is converted to calcium oxide

which is a very useful substance.

(a) Calculate the formula mass (Mr) of calcium carbonate.

.....................................................................................................................................

Mr of calcium carbonate = ...............................................

(2)

(b) About 60 million tonnes of calcium oxide is made in Britain each year. Calculate the mass of calcium carbonate needed to make this amount of calcium oxide.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

Mass of calcium carbonate needed = .............................. million tonnes (4)

(c) Water is added to some of the calcium oxide produced in a process known as ‘slaking’. The product of this reaction is used to make plaster.

CaO(s)

+ H2O

(1)→ Ca(OH)

2(s)

(i) Give the chemical name of Ca(OH)2.

.......................................................................................................................... (1)

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(ii) What is the physical state of the Ca(OH)2 formed in the reaction?

.......................................................................................................................... (1)

(Total 8 marks)

Q23. The salt sodium hydrogen phosphate (Na2HPO

4) is used as a softening agent in

processed cheese.

It can be made by reacting phosphoric acid (H3PO

4) with an alkali.

(a) Complete the name of an alkali that could react with phosphoric acid to make sodium hydrogen phosphate.

....................................... hydroxide (1)

(b) What is the name given to a reaction in which an acid reacts with an alkali to make a salt?

..................................................................................................................................... (1)

(c) How would the pH change when alkali is added to the phosphoric acid solution?

.....................................................................................................................................

..................................................................................................................................... (1)

(d) What ions are present when any acid is dissolved in water?

..................................................................................................................................... (1)

(e) What ions are present when any alkali is dissolved in water?

..................................................................................................................................... (1)

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(f) Write a chemical equation for the reaction which takes place between the ions you have named in (e) and (f).

..................................................................................................................................... (1)

(Total 6 marks)

Q24. Ammonia and nitric acid are both important chemicals. Nitric acid is made from ammonia.

The charts below show substances made from ammonia and nitric acid.

(a) Use the charts to help you answer these questions.

(i) What is the main use of both ammonia and nitric acid?

.......................................................................................................................... (1)

(ii) Work out the percentage of ammonia used to make nitric acid.

Percentage = ........................ % (1)

(iii) 100 million tonnes of ammonia are made in the world each year.

How much of this ammonia is used to make nylon?

.......................... million tonnes (1)

(b) The word equations below show how nitric acid is made.

1. nitrogen + hydrogen → ammonia

2. ammonia + oxygen → nitrogen monoxide + water

3. nitrogen monoxide + oxygen → nitrogen dioxide

4. nitrogen dioxide + water → nitric acid

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Use the word equations to help you answer these questions.

(i) From which two elements is ammonia made?

......................................................... and ......................................................... (1)

(ii) Name two of the raw materials needed to make nitric acid.

......................................................... and ......................................................... (2)

(c) A large amount of nitric acid is reacted with ammonia to make a fertiliser.

nitric acid + ammonia → fertiliser

(i) The reaction is a neutralisation reaction.

What type of chemical must ammonia be?

........................................................................................................................... (1)

(ii) Complete the chemical name for the fertiliser made from ammonia and nitric acid.

ammonium .................................................... (1)

(iii) The reaction of nitric acid with ammonia is exothermic.

Name the piece of equipment you could put into the solution to prove that the reaction is exothermic.

........................................................................................................................... (1)

(Total 9 marks)

Q25. This article appeared in a newspaper.

(a) The balanced chemical equation shows the reaction between steel and hydrochloric acid.

Fe(s) + 2HCl(aq) → FeCl2(aq) + H

2(g)

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(i) Which metal in steel reacted with the hydrochloric acid?

........................................................................................................................... (1)

(ii) The gas released was described as explosive. Explain why.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(b) In the factory hydrogen chloride is manufactured by reacting hydrogen with chlorine. Hydrochloric acid is formed when hydrogen chloride forms a solution in water.

(i) Water was sprayed on the steel and hydrochloric acid. This slowed the rate of reaction. Explain why.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) It would have been better to neutralise the acid with an alkali rather than to just add water. Hydrochloric acid can be neutralised by reaction with sodium hydroxide. Complete the ionic equation for the neutralisation reaction.

(aq) + (aq) → H2O(l)

(2)

(iii) In the factory the acid leak was neutralised with slaked lime, Ca(OH)2, and not

sodium hydroxide, NaOH. Suggest why.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 10 marks)

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Q26. Calcium tablets are taken to build and maintain strong bones and teeth.

(a) These tablets react with hydrochloric acid in the stomach.

CaCO3( ) + 2HCl(aq) → CaCl

2( ) + H

2O( ) + CO

2( )

(i) Add all these missing state symbols to the balanced chemical equation.

(2)

(ii) The calcium salt that is formed is absorbed during digestion. What is the name of the calcium salt?

...........................................................................................................................

........................................................................................................................... (1)

(b) The volume of carbon dioxide produced by one calcium tablet in the stomach can be found as shown.

The volume of carbon dioxide was recorded every 30 seconds until the reaction stopped.

Time in seconds 0 30 60 90 120 150 180 210 240

Volume of gas in cm3

0 24 36 46 52 56 59 60 60

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(i) Complete the graph of these results.

(3)

(ii) Describe one way in which this reaction can be made to go faster.

...........................................................................................................................

........................................................................................................................... (1)

(iii) A calculation, using the mass of this tablet, showed that 80 cm3 of carbon dioxide would be produced if the tablet was pure calcium carbonate. What do the results show about the purity of the tablet? Explain your answer by calculating the purity of this tablet.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(Total 10 marks)

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Q27. Many everyday substances can be classified as acids, bases or salts. For example, car batteries contain sulphuric acid, oven cleaners contain sodium hydroxide and table salt contains sodium chloride.

(a) A solution of each of these substances was tested with universal indicator.

Solution Colour of universal indicator

Sulphuric acid (H2SO

4) red

Sodium hydroxide (NaOH) purple

Sodium chloride (NaCl) green

(i) Explain how these universal indicator colours and the corresponding pH values could be used to identify each of these solutions.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(ii) Name and give the formula of the ion which causes the solution to be acidic.

Name of ion ..................................................................................................

Formula of ion ................................................................................................. (2)

(b) Sodium chloride can be made by reacting sodium hydroxide with hydrochloric acid in the presence of an indicator.

(i) What is the name of this type of reaction?

.......................................................................................................................... (1)

(ii) Write a balanced chemical equation for this reaction.

..............(aq) + ..............(aq) → ..............(aq) + ..............(l) (2)

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(c) The atomic number for sodium is 11 and for chlorine is 17.

(i) Complete the diagrams to show the electron arrangements for a sodium atom and a chlorine atom.

(2)

(ii) These atoms form different particles by one electron transferring from the sodium atom to the chlorine atom. What is the name given to the particles formed?

........................................................................................................................... (1)

(iii) Why do these sodium and chloride particles bond?

...........................................................................................................................

........................................................................................................................... (1)

(d) Sodium chloride solution is electrolysed to form three products, hydrogen, chlorine and sodium hydroxide.

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Describe how each of these products are formed.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 15 marks)

Q28. Acids and bases are commonly found around the home.

(a) Baking powder contains sodium hydrogencarbonate mixed with an acid.

(i) When water is added, the baking powder releases carbon dioxide. How could you test the gas to show that it is carbon dioxide?

Test ..................................................................................................................

Result of test .................................................................................................... (2)

(ii) Complete and balance the chemical equation for the reaction of sodium hydrogencarbonate with sulphuric acid.

NaHCO3 + H

2SO

4 → ....................... + ........................ + ..................

(2)

(b) Indigestion tablets contain bases which cure indigestion by neutralising excess stomach acid.

(i) One type of indigestion tablet contains magnesium hydroxide. This base neutralises stomach acid as shown by the balanced chemical equation.

Mg(OH)2 + 2HCl → MgCl

2 + 2H

2O

Write a balanced ionic equation for the neutralisation reaction.

.......................................................................................................................... (2)

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(ii) How does the pH in the stomach change after taking the tablets?

.......................................................................................................................... (1)

(c) Ammonium sulphate is used as a lawn fertiliser.

Using ammonia solution, describe how you would make the fertiliser ammonium sulphate.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 10 marks)

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Q29. A student investigated the electrolysis of lead bromide.

Lead bromide was placed in the tube and the circuit was switched on. The light bulb did not light up.

The tube was heated and soon the bulb lit up. The observations are shown in the table.

Positive electrode Negative electrode

red-brown gas silver liquid

(a) What is meant by electrolysis?

.................................................................................................................................... (2)

(b) Why did the lead bromide conduct electricity when the tube was heated?

.................................................................................................................................... (1)

(c) Name the substances formed at the:

positive electrode; .....................................................................................................

negative electrode. .................................................................................................... (2)

(d) Suggest one safety precaution that should be taken during this investigation.

.................................................................................................................................... (1)

(Total 6 marks)

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Q30. A student tried to make some magnesium sulphate. Excess magnesium was added to dilute sulphuric acid. During this reaction fizzing was observed due to the production of a gas.

(i) Complete and balance the chemical equation for this reaction.

..................... + H2SO

4 → ....................... + ........................

(3)

(ii) At the end of the reaction the solution remaining was filtered. Why was the solution filtered?

..................................................................................................................................... (1)

(iii) The filtered solution was left in a warm place.

Explain why the filtered solution was left in a warm place.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 6 marks)

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Q31. Bordeaux Mixture controls some fungal infections on plants.

A student wanted to make some Bordeaux Mixture.

(a) The student knew that calcium oxide could be made by heating limestone. Limestone contains calcium carbonate, CaCO

3.

(i) Write the word equation for this reaction.

........................................................................................................................... (1)

(ii) What type of reaction is this?

........................................................................................................................... (1)

(b) The student knew that copper sulphate, CuSO4, could be made by the following general

reaction.

acid + base → salt + water

(i) What type of reaction is this?

........................................................................................................................... (1)

(ii) The base used is copper oxide. Name and give the chemical formula of the acid used.

Name ................................................................................................................

Chemical formula ............................................................................................. (2)

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(c) The student wrote about how the copper sulphate was made.

“Some of the acid was warmed. Copper oxide was added. The mixture was stirred. More copper oxide was added until no more would react. The mixture was then filtered.”

(i) Why was the acid warmed?

...........................................................................................................................

........................................................................................................................... (1)

(ii) Copper oxide was added until no more would react. Explain why.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(iii) The filtration apparatus is shown.

Describe and explain what happens as the mixture is filtered.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 10 marks)

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Q32. (a) The diagram shows one way of making crystals of copper sulphate.

(i) Why was the solution filtered?

.......................................................................................................................... (1)

(ii) How could you make the crystals form faster from the copper sulphate solution?

.......................................................................................................................... (1)

(iii) The chemical equation is shown for this reaction.

CuO(s) + H2SO

4(aq) → CuSO

4(aq) + H

2O(l)

In the chemical equation what does (aq) mean?

.......................................................................................................................... (1)

(b) Blue copper sulphate crystals go white when warmed. How could you use the white copper sulphate as a test for water?

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (2)

(Total 5 marks)

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Q33. Explain, in terms of ions and molecules, what happens when any acid reacts with any alkali.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

............................................................................................................................................... (Total 3 marks)

Q34. The information in the box is about the preparation of copper sulphate crystals.

Step 1 Add a small amount of black copper oxide to some hot dilute sulphuric acid, and stir.

Step 2 Keep adding copper oxide until it is in excess.

Step 3 Remove the excess copper oxide to leave blue copper sulphate solution.

Step 4 Evaporate the copper sulphate solution until it is saturated.

Step 5 Leave the saturated solution of copper sulphate to cool. Blue copper sulphate crystals form on cooling.

Step 6 Remove the crystals from the solution remaining.

Step 7 Dry the blue crystals on a piece of filter paper.

(i) Suggest a reason for using excess copper oxide in Step 2.

.....................................................................................................................................

..................................................................................................................................... (1)

(ii) Suggest how the excess copper oxide can be removed from the solution in Step 3.

.....................................................................................................................................

..................................................................................................................................... (1)

(iii) What is meant by the term saturated solution?

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

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(iv) Why do crystals form when a hot saturated solution cools?

.....................................................................................................................................

..................................................................................................................................... (1)

(v) Suggest why the blue crystals are dried in Step 7 using filter paper instead of by heating.

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 6 marks)

Q35. Salts can be prepared by the reaction of acids with alkalis.

(a) (i) The reactions of acids with alkalis can be represented by the equation below. Choose a substance from the box to complete the equation.

acid + alkali → salt + .......................................................... (1)

(ii) Draw a ring around the word which best describes the reaction.

displacement neutralisation oxidation reduction (1)

carbon dioxide hydrogen oxygen water

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(b) Sodium sulphate is an important salt.

The table gives a list of some substances.

Put a tick ( ) next to the names of the acid and the alkali that would react to make sodium sulphate.

(2) (Total 4 marks)

Substances ( )

Hydrochloric acid

Nitric acid

Potassium sulphate

Sodium hydroxide

Sodium nitrate

Sulphuric acid

Q36. The following passage is about the preparation of lead iodide, an insoluble salt.

An excess of potassium iodide in solution was shaken with some lead nitrate solution in a test tube.

The lead iodide precipitate was separated from the mixture and then washed several times with water.

The lead iodide was dried and then placed in a bottle.

(a) Suggest a reason why excess potassium iodide was used.

.....................................................................................................................................

..................................................................................................................................... (1)

(b) What word used in the passage shows that lead iodide is insoluble?

.................................................................................................................................... (1)

(c) Suggest how lead iodide can be separated from the mixture.

....................................................................................................................................

.................................................................................................................................... (1)

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(d) Why was the lead iodide washed with water?

....................................................................................................................................

.................................................................................................................................... (1)

(e) Suggest a method which could be used to dry this lead iodide.

....................................................................................................................................

.................................................................................................................................... (1)

(f) Lead compounds are toxic.

Suggest a suitable safety precaution that should be taken when using toxic substances in laboratories.

.................................................................................................................................... (1)

(Total 6 marks)

Q37. Ammonium nitrate and potassium chloride are both salts. They can be made by neutralisation reactions.

Choose substances from the box to complete the word equations for the formation of these two salts.

ammonia + ........................................ → ammonium nitrate + water

.................................. + hydrochloric acid → potassium chloride + .......................... (Total 3 marks)

ammonia hydrochloric acid nitric acid

potassium nitrate water potassium hydroxide

Q38. Neutralisation reactions can be used to make salts.

(a) Write an ionic equation for a neutralisation reaction, including state symbols.

..................................................................................................................................... (2)

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(b) Ammonium nitrate is a salt used as a fertiliser.

(i) Ammonium nitrate is made by mixing two solutions. Name these solutions.

......................................................... and ......................................................... (1)

(ii) Hazard information about ammonium nitrate states:

• it is not itself a fire hazard (does not burn);

• it must not be allowed to come into contact with combustible materials such as fuels because it can cause these to catch fire.

Suggest why ammonium nitrate helps other substances to burn.

..........................................................................................................................

.......................................................................................................................... (1)

(Total 4 marks)

Q39. Nitric acid can be neutralised by alkalis to make salts.

(i) The salt called potassium nitrate can be made from nitric acid.

Complete the word equation for this neutralisation reaction. Choose the correct substances from the box.

nitric acid + ................................ →potassium nitrate + ................................ (2)

hydrogen oxygen potassium chloride

potassium hydroxide water

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(ii) Ammonium nitrate is another salt made from nitric acid.

Which one of the following is the main use of ammonium nitrate? Draw a ring around your answer.

dye fertiliser plastic fuel (1)

(iii) Complete this sentence by choosing the correct ion from the box.

The ion that makes solutions acidic is ............................................................ . (1)

(Total 4 marks)

H+ NH4

+ NO3

– O2– OH–

Q40. Copper sulfate (CuSO4) is a salt that has many uses.

An aqueous solution of copper sulfate can be made by reacting copper oxide (CuO) with an acid.

(a) (i) Name this acid. ............................................................................................... (1)

(ii) Write a balanced symbol equation, including state symbols, for this reaction.

......................................................................................................................... (2)

(b) Copper oxide reacts much faster with acid at 40 °C than at 20 °C.

Explain why in terms of particles.

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

................................................................................................................................... (2)

(Total 5 marks)

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Q41. This label was taken from a cola drink.

The pH of this drink is 2.5.

(a) (i) Which one of the ingredients in the cola drink causes the low pH?

.......................................................................................................................... (1)

(ii) Draw a ring around the name of the ion that gives the cola drink its low pH.

chloride hydrogen hydroxide sodium (1)

(b) The preservative used in the cola drink is sodium benzoate. Sodium benzoate is made using two chemical reactions.

Reaction 1 Methylbenzene is reacted with oxygen, with the help of a catalyst, to form benzoic acid.

Reaction 2 Benzoic acid is neutralised by sodium hydroxide solution to form sodium benzoate and

water.

(i) How does the catalyst help reaction 1?

..........................................................................................................................

.......................................................................................................................... (1)

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(ii) Reaction 1 has a high atom economy.

The table lists several statements. Put a tick ( ) next to the one statement which best describes a high atom economy.

(1)

Statement ( )

All the atoms used are cheap.

Most of the starting materials end up as useful products.

Only a small number of atoms are used in the reaction.

(iii) Reaction 2 is a neutralisation reaction.

Complete the equation by writing the formula of the product.

H+ + OH– → ...................

(1) (Total 5 marks)

Q42. Photographic film often contains silver bromide. Silver bromide is changed by light to form silver which appears as a black solid. This darkens the photographic film.

A photographic film can be made by coating thin transparent plastic with a gel containing silver bromide.

The main steps in making this photographic film are as follows:

Step 1 Gelatine is dissolved in warm water to make a solution.

Step 2 Compound A, a soluble compound which contains bromide ions, is dissolved into this solution.

Step 3 The lights are turned out in the darkroom.

Step 4 Compound B, a soluble compound which contains silver ions, is dissolved in water.

Step 5 The solution of compound B is added to the solution containing compound A and gelatine. Solid silver bromide is formed.

Step 6 The warm mixture is poured onto thin, transparent plastic film.

Step 7 The mixture sets to form a gel containing solid silver bromide.

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(a) The table below gives information about the solubility of some compounds.

Use the table to help you to name suitable compounds for A and B.

Compound A ..............................................................................................................

Compound B .............................................................................................................. (2)

SOLUBLE INSOLUBLE

All sodium and potassium salts

All nitrates

Most chlorides, bromides and iodides Silver and lead chlorides, bromides and iodides

Most sulfates Lead sulfate and barium sulfate

Sodium, potassium and ammonium carbonates

Most other carbonates

(b) Suggest why the lights are turned out at step 3 in this method of making a photographic film.

....................................................................................................................................

.................................................................................................................................... (1)

(c) What type of chemical reaction takes place when the compounds are mixed in step 5?

.................................................................................................................................... (1)

(d) The photographic film is placed in a camera and a picture is taken. Where light hits the photographic film the silver ions (Ag+) are changed into silver metal (Ag).

Explain why this reaction is a reduction.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (2)

(Total 6 marks)

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Q43. (a) Write a balanced symbol equation for the reaction between magnesium (Mg) and oxygen (O

2) to form magnesium oxide (MgO).

..................................................................................................................................... (1)

(b) The diagram shows the electronic structure of a magnesium atom. The atomic (proton) number of magnesium is 12.

Magnesium atom

Draw a similar diagram to show the electronic structure of an oxygen atom. The atomic (proton) number of oxygen is 8.

(1)

(c) Magnesium ions and oxide ions are formed when magnesium reacts with oxygen.

The diagram shows the electronic structure of an oxide ion.

Oxide ion

Draw a similar diagram to show the electronic structure of a magnesium ion.

(1)

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(d) Magnesium oxide is a white solid with a high melting point.

Explain how the ions are held together in solid magnesium oxide.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(e) Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralises some of the hydrochloric acid in the stomach.

Complete the word equation for the reaction between magnesium oxide and hydrochloric acid.

hydrochloric acid + magnesium oxide → ...................... + water. (1)

(Total 6 marks)

Q44. Distress flares are used to attract attention in an emergency.

Flares often contain magnesium. Magnesium burns to form magnesium oxide.

(a) The distress flare burns with a bright flame because the reaction is very exothermic.

Complete the following sentence using the correct words from the box.

An exothermic reaction is one which .......................................................................... (1)

gives out heat stores heat takes in heat

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(b) The diagram shows the electronic structure of a magnesium atom. The atomic (proton) number of magnesium is 12.

Magnesium atom

The atomic (proton) number of oxygen is 8.

Which diagram, A, B, C or D, shows the electronic structure of an oxygen atom?

Diagram .............................. (1)

(c) Magnesium ions and oxide ions are formed when magnesium reacts with oxygen. The diagram shows the electronic structure of an oxide ion.

Oxide ion

Which diagram, J, K, L or M, shows the electronic structure of a magnesium ion?

Diagram .............................. (1)

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(d) Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralises some of the hydrochloric acid in the stomach.

Draw a ring around the name of the salt formed when magnesium oxide reacts with hydrochloric acid.

magnesium chloride magnesium hydroxide magnesium sulfate (1)

(Total 4 marks)

Q45. Read the article and then answer the questions that follow.

Hydrogen fuel for cars?

Hydrogen is an excellent fuel. It can be made by the electrolysis of potassium hydroxide solution.

Hydrogen gas can be stored under pressure in a cylinder but a leak of the gas could cause an explosion.

It has been found that lithium nitride can absorb and then release large volumes of hydrogen. A chemical reaction takes place between the hydrogen and the lithium nitride. The hydrogen is held in the resulting compounds by chemical bonds.

The problem is that the rate at which hydrogen is absorbed and then released from normal sized particles of lithium nitride is slow.

Recently scientists have made ‘nanosized’ particles of lithium nitride. These particles absorb hydrogen in the same way as normal sized lithium nitride particles. The ‘nanosized’ particles have the advantage that they absorb and release the hydrogen much faster when needed in the fuel cell.

It is hoped that ‘nanosized’ particles of lithium nitride may provide a safe method of storing hydrogen in the future.

(a) Hydrogen is produced at the negative electrode during the electrolysis of potassium hydroxide solution.

(i) Why are hydrogen ions attracted to the negative electrode?

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

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(ii) Potassium ions are also attracted to the negative electrode.

Explain why hydrogen gas is formed but not potassium.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(b) Lithium nitride is made by reacting lithium with nitrogen.

Balance the equation for this reaction.

.......... Li + N2 → .......... Li

3N

(1)

(c) (i) The equation for the reaction of lithium nitride with hydrogen is:

Li3N + 2H

2 LiNH

2 + 2LiH

What feature of this reaction allows the hydrogen to be released?

...........................................................................................................................

........................................................................................................................... (1)

(ii) Hydrogen stored in a fuel tank filled with lithium nitride would be safer in an accident than a cylinder full of hydrogen.

Suggest and explain why.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(d) Lithium nitride is an ionic compound which contains lithium ions (Li+) and nitride ions (N3–).

(i) The formation of a lithium ion from a lithium atom is an oxidation reaction.

Explain why.

...........................................................................................................................

........................................................................................................................... (1)

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(ii) The diagram shows the electronic structure of a nitrogen atom.

Complete the diagram below to show the electronic structure of a nitride ion (N3–).

(1)

(Total 8 marks)

Q46. (a) Citric acid produces hydrogen ions in aqueous solution.

These ions can be represented as H+(aq).

Complete this sentence.

The (aq) means that the acid has been dissolved in .................................................. . (1)

(b) The diagram represents a hydrogen atom, H.

Use the diagram to explain why a hydrogen ion, H+, is a proton.

.....................................................................................................................................

..................................................................................................................................... (1)

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(c) Citric acid is a weak acid.

Draw a ring around the correct answer to complete the sentence.

(1)

has a low boiling point.

The word weak means that the acid is dilute.

is partially ionised in water.

(d) A student measured the pH of four acids, A, B, C and D.

The acids were the same concentration. The same quantity of magnesium ribbon was added to each of the acids. The volume of gas produced after 5 minutes was recorded.

The results are shown in the table.

Acid pH Volume of gas in cm3

A 2 18

B 5 6

C 1 24

D 4 12

(i) State one way in which the student made sure that the experiment was fair.

........................................................................................................................... (1)

(ii) Use the results to arrange the acids, A, B, C and D in order of decreasing acid strength.

Most acidic ........................................................................................ Least acidic. (1)

(e) When acids react with alkalis, the hydrogen ions from the acid react with the hydroxide ions from the alkali.

(i) Which one of the following represents the formula of a hydroxide ion?

Draw a ring around your answer.

H– O– OH–

(1)

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(ii) Draw a ring around the correct answer to complete the sentence.

(1) (Total 7 marks)

acidic.

A solution with more hydrogen ions than hydroxide ions is alkaline.

neutral.

Q47. Ammonia has the formula NH3

The diagrams show how electrons are arranged in nitrogen and hydrogen atoms.

(a) Draw a diagram to show how the electrons are arranged in an ammonia molecule.

You need only show the electrons in the highest energy level.

(2)

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(b) Ammonia is a gas at room temperature.

Explain why ammonia has a low boiling point.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(c) Ammonia dissolves in water to form a solution with a pH of about 10.

(i) Name the ion in the ammonia solution that causes the pH of 10.

...................................................... ion (1)

(ii) Ammonium nitrate is made by reacting ammonia with an acid.

Name the acid.

...................................................... acid (1)

(d) Instant cold packs are used to treat sports injuries.

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One type of cold pack has a plastic bag with water inside. Inside the bag is a smaller bag containing solid ammonium nitrate.

The outer bag is squeezed so that the inner bag bursts. The pack is shaken and quickly gets cold as the ammonium nitrate dissolves in the water.

Explain why the bag gets cold.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(Total 8 marks)

Q48. Waste water from some industrial processes contains harmful metal ions, such as chromium ions. Harmful metal ions must be removed from the water before the water is returned to a river.

(a) A method of removing chromium ions (Cr3+) from water is represented by this equation.

Balance the equation.

Cr3+(aq) + ...........OH–(aq) → Cr(OH)3(s)

(1)

(b) Suggest a suitable chemical that could be added to the water to provide the OH– ions.

........................................................................................................................ (1)

(c) Explain how chromium ions are removed from the water.

........................................................................................................................

........................................................................................................................ (1)

(Total 3 marks)

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Q49. In this question you will get marks on using good English, organising information clearly and using specialist terms correctly.

Copper sulfate crystals can be made from copper oxide powder and dilute sulfuric acid.

Describe a method to make copper sulfate crystals from copper oxide and dilute sulfuric acid.

For the method you should include:

• the names of the pieces of apparatus used • a risk assessment.

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

................................................................................................................................. (Total 6 marks)

Q50. Waste water from some industrial processes contains harmful metal ions, such as chromium ions. These ions must be removed from the water before the water is returned to a river.

The equation shows a method of removing chromium ions from water.

CrCl3(aq) + 3NaOH(aq) → Cr(OH)

3(s) + 3NaCl(aq)

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(a) This type of reaction is called a precipitation reaction.

Describe what happens in a precipitation reaction

........................................................................................................................

........................................................................................................................ (1)

(b) Complete the name of the substance with the formula NaOH.

Sodium ........................................ (1)

(c) Draw a ring around the method that could be used to separate the Cr(OH)3(s) from the

water.

electrolysis filtration neutralisation oxidation (1)

(d) It is important to remove chromium ions from water before it is returned to a river.

Suggest why.

........................................................................................................................

........................................................................................................................ (1)

(Total 4 marks)

Q51. (a) Ammonia has the formula NH3. It is made from nitrogen and hydrogen.

How many atoms are in an ammonia molecule? .......................................... (1)

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(b) The diagrams show the electron arrangement in nitrogen and hydrogen.

Which diagram below, A, B, C or D, represents an ammonia molecule?

Write your answer in the box.

Diagram (1)

(c) Ammonia dissolves in water to form a solution with a pH of 10.

What does this pH value tell you about ammonia solution?

........................................................................................................................ (1)

(d) In industry a large amount of ammonia is neutralised by an acid to make ammonium nitrate.

(i) What type of substance is ammonium nitrate?

Tick ( ) one box.

(1)

acid

alkali

base

salt

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(ii) Which acid is added to ammonia to make ammonium nitrate?

Tick ( ) one box.

(1)

hydrochloric

citric

nitric

sulfuric

(iii) Draw a ring around the main use of ammonium nitrate.

fertiliser lubricating oil medicine plastic (1)

(e) Instant cold packs are used to treat sports injuries.

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One type of cold pack has a plastic bag containing water. Inside the bag is a smaller bag containing ammonium nitrate.

The outer bag is squeezed so that the inner bag bursts. The ammonium nitrate dissolves in the water. This process is endothermic.

Explain why the bag becomes cold.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................ (2)

(Total 8 marks)

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M1. (a) oxygen / O2 (do not allow air)

for 1 mark 1

(b) idea that (it is a) catalyst / it increases the rate of reaction

for 1 mark 1

(c) water H2O and oxygen / O

2 (need both) (in either order)

for 1 mark 1

(d) ammonia / NH3 (do not allow ammonium)

(allow ammonium hydroxide / NH4OH or ammonia solution)

nitric acid / NHO3

in any order for 1 mark each 2

(e) 14 + 4 + 14 + 48 or Mr = 80

gains 1 mark

but or 35%

gains 2 marks 2

[7]

M2. (a) lead chloride } in any order potassium nitrate }

for 1 mark each 2

(b) lead chloride is solid / a precipitate potassium nitrate is aqueous / in solution / dissolves in water NOT liquid

for 1 mark each 2

(Accept ratio of molecular KNO3 : PbC1

2 is 2:1 for 2 marks)

(do not accept relative number of atoms in each compound)

One is a solid, one is a solution – worth 1 mark [4]

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M3. • correct use of react/reaction/reactants NOT mixed added to join/combine/displace NOT equals

• correct use of produce/products/gives/forms/makes/creates

• reactants correctly identified

• products correctly identified

(copper oxide reacts with sulphuric acid to produce copper sulphate and water, will be awarded all 4 marks)

for 1 mark each

Reactants must be correctly identified for ‘react’ mark to be given. Similarly for products [4]

M4. (a) (i) lead chloride/product of lead + chloride ions is insoluble (in water)

for 1 mark 1

(ii) Pb2+ + 2C1¯ → PbC12 *(s)

(allow (Pb)2+ 2 (C1–) )

formula solid state symbol balancing for 1 mark each

3

(b) copper hydroxide Cu(OH)2

each for 1 mark

lead sulphate PbSO4

each for 1 mark

no precipitate for 1 mark

Allow 1 mark for correct formula Na2SO

4 in (i)

Allow 1 mark for correct formula Mg (NO3)

2 in (ii)

0 marks for any formula in (iii) 5

[9]

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M5. (i) carbon dioxide (allow CO2)

for 1 mark 1

(ii) sodium nitrate (accept correct formula) for 1 mark

1 [2]

M6. (a) (i) sodium ions and chloride ions

(allow sodium chloride/salt) [not “chlorine”] for 1 mark 1

(ii) sodium ions and chloride ions (allow sodium chloride/salt) for 1 mark

H + ions (allow hydrochloric acid) for 1 mark

2

(b) H+ + OH– → H2O [N.B Na+ and Cl– may also be present]

H+ ions from acid

OH– ions from alkali

each for 1 mark

[N.B First mark lost if changes on ions not shown] 3

[6]

##

(a) sodium ions and chloride ions (not chlorine) allow sodium chloride/salt/common salt

for 1 mark 1

(b) H+ + OH– →H2O

H+ from (hydrochloric) acid

OH- from alkali/sodium hydroxide lose 1 mark if no charge shown disregard other ions

each for 1 mark 3

[4]

-

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M8. (i) hydrogen, hydroxide and sulphate

all three and no others any order do not credit any formula(e)

1

(ii) the anode is positive 1

(so) only the negative ions are attracted to it or (so) only the hydroxide ions and the sulphate ions are attracted (to it) or (so) only the anions are attracted (to it)

1

(iii) 2H2O + O

2 + 4e–

1 [4]

M9. (a) (i) 8

ammonia do not credit ammonium

sulphuric acid do not credit just sulphuric; credit sulfuric acid do not credit hydrogen sulphate

3

(ii) (as a) fertiliser 1

(iii) nitric (acid) accept HNO

3 if correct in every detail

1

(b) (i) chemical change (in which) or under suitable conditions

1

product(s) can be converted to reactant(s) or direction of reaction can be reversed or equilibrium can be achieved do not credit reaction can be reversed

1

(ii) air or (the) atmosphere

1

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(iii) made of atoms 1

which are all the same credit the idea that the particles (in an element) are all the same even if the name of the particles (the first mark) is incorrect or which have the same number of protons or which have the same atomic number / proton number it cannot be broken down into anything simpler (2) marks

1 [10]

M10. NOTE

In this question and throughout the Paper, if the name of a chemical is asked for, then the formula is acceptable only if it is correct in every detail. If the name is correct and the candidate has tried to be ‘helpful’ by giving, in addition, an incorrect version of the formula, then this is acceptable provided it does not lead to ambiguity.

(i) nitric (acid) accept HN0

3

1

(ii) sulphuric (acid) accept H

2SO

4

1

(iii) heat given out or temperature rise or energy given out or steam do not credit just ‘use a thermometer’ do not credit just 'change in temperature'

1

(iv) neutralisation accept neutralise accept neutral accept formation of salt or water do not credit exothermic

1 [4]

M11. (a) ammonium nitrate

accept NH4NO

3

do not accept ammonia nitrate 1

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(b) different reactions need different catalysts 1

(c) they are used over and over again accept they are reused accept they are not used up accept they are not changed recycling is neutral

1

(d) any two from

they speed up reactions

they reduce energy requirements accept allow reactions to take place at a lower temperature

they reduce costs accept make process more economic

2

(e) (high pressure) increases the frequency of collisions

accept more collisions move faster is neutral

1

this increases the rate of reaction accept ‘more successful collisions’ for 2 marks

1 [7]

M12. (a) nitrogen

accept N or N2

1

(b) the reaction is exothermic accept the reaction releases heat energy

1

(c) water accept H

2O or hydrogen oxide

1

(d) with ammonia and nitric acid 1

neutralisation accept a correct description of reacting (ammonia and nitric acid)

1 [5]

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M13. (a) (i) 2 Mg + O2 → 2 MgO

both 2s needed

allow O2 or any correct multiple

1

(ii) solid 1

gas 1

(b) MgCl2 / C1

2Mg

do not accept MG mg mG CL cl cL ignore charges

1 [4]

M14. sodium nitrate 1

NaNO

3

do not credit lower case N or O, upper case A 1

potassium sulphate 1

K2SO

4

accept potassium hydrogen sulphate or KHSO4

do not credit lower case K, S or O ignore charges on ions

1 [4]

M15. (a) NO2 / 2NO

2(g) / Nitrogen dioxide

for one mark 1

(b) particles of gas move / they move

reject spread out particles move randomly / mix / go between air molecules / diffusion

any two for 1 mark each 2

(c) faster reaction / more surface area (not smaller pieces) for one mark

1

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(d) (i) either lower temperature / particles move slower fewer collisions (owtte) / less energetic collisions / owtte or acid diluted (owtte) fewer collisions (owtte)

for 1 mark each 2

(ii) alkali neutralises the acid / stops the reaction or water will only slow the reaction not stop it

either for 1 mark 1

[7]

M16. (i) sulphuric acid / H2SO

4

accept sulfuric 1 for one mark 1

(ii) exothermic for one mark

1

(iii) Na2SO

4 / (Na)

2SO

4 / Na

2(SO

4) / (Na+)

2SO

4

2–

for one mark lower case O(Na

2SO

4) not accepted / tops of subscripted letters

should be in line or lower than lower case letters of symbols 1

[3]

##

(a) (2) : (6) : (2) All 3 correct gains 2 marks 2 correct gains 1 mark

2

(b) no water present/moist air cannot enter/do not thoroughly mix/ must be in solution etc.

for 1 mark 1

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(c) (i) hydroxide (ion) / OH–

for 1 mark 1

(ii) hydrogen (ion) / H+

for 1 mark 1

(iii) water/H2O/hydrogen oxide

for 1 mark 1

[6]

##

(a) potassium / K for 1 mark

1

(b) carbon dioxide / CO2

for 1 mark 1

(c) losing electrons gaining electrons

for 1 mark each 4

(d) (i) power supply, (not mains) beaker containing solution, (inert) electrodes and circuit ammeter or bulb/ (or see bubbling etc. at electrodes written by drawing)

for 1 mark each 4

(ii) reading on ammeter/bulb lights / (solution) conducts (electricity) bubbling / gas produced hydrogen produced chlorine / oxygen produced ions move to electrodes (must be linked to ions move) negative ions move to the positive electrode and/or positive ions move to the negative electrode negative ions lose electrons and/or positive ions gain electrons

any 3 for 1 mark each 3

[13]

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M19. (a) (i) Na2CO

3 or (Na+)

2 CO

3

2– must be completely correct

for 1 mark 1

(ii) (1) decomposition of limestone or decomposition of coal or decomposition of sodium hydrogen carbonate (owtte.) allow equations even if not correctly balanced

any 1 for 1 mark 1

(2) breakdown/split up not decomposed by heat

for 1 mark each 2

(iii) carbon dioxide or ammonia [CO2] or [NH

3]

for 1 mark 1

(b) (i) zinc carbonate or zinc hydroxide allow formulae if completely correct

for 1 mark 1

(ii) (zinc carbonate) is insoluble (in water) ((i) and (ii) are independent marks)

for 1 mark 1

[7]

M20. (a) (i) hydrogen/H2

for 1 mark 1

(ii) i.e. 2Cl¯ -2e– →Cl2

for 1 mark 1

(iii) hydroxide or OH–

for 1 mark 1

(iv) sodium hydroxide/caustic soda/NaOH/bleach/ chemical name of bleach

for 1 mark 1

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(b) (i) Na2CO

3 or (Na+)

2 CO

3

2–

for 1 mark 1

(ii) coal water/H

2O

limestone/CaCO3/calcium carbonate

any one for 1 mark 1

(iii) calcium chloride/CaCl2/sodium hydrogen

carbonate/NaHCO3

for 1 mark 1

(iv) decomposition/heating of limesstone decomposition/heating of coal decomposition/heating of sodium hydrogen carbonate

any 1 for 1 mark 1

described change e.g. NaHCO3 → Na

2 CO

3

(Use judgement) breakdown (owtte.) by heat

for 1 mark each 2

(v) carbon dioxide/CO2 or ammonia/NH

3

for 1 mark 1

(c) (i) zinc carbonate/ZnCO3/zinc

hydroxide/Zn(OH)2

for 1 mark 1

(ii) It is insoluble zinc carbonate is insoluble in water

for 1 mark 1

[13]

M21. (a) (i) H+ + OH- → H2 O/H

3O+ + OH- → 2H

2 O

for 1 mark 1

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(ii) 1 point from e.g. smaller bits bigger surface area faster reaction dissolve faster more particles open to attack by acid

any 1 for 1 mark 1

(iii) MgCO3 or MG2+CO

3

2- or CO3 Mg

for 1 mark 1

(b) (i) 2 HCl for 1 mark

1

(ii) aqueous/dissolved in water (not in solution) for 1 mark

1

(iii) CO2/gas evolved/gas has mass

for 1 mark 1

(c) (i) plotting points scales curve labelling axes including units

for 1 mark each 4

(d) faster same final mass

for 1 mark each 2

[12]

M22. (a) 40 + 12 + (3 × 16) = 100

each for 1 mark 2

(b) Mr of CaO = 56

for 1 mark

mass required = 60 × 100/56 for 2 marks

= 107.1 for 1 mark

4

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(c) (i) calcium hydroxide 1

(ii) solid 1

[8]

M23. (a) sodium 1

(b) neutralisation 1

(c) increase/inc. number 1

(d) H+

1

(e) OH–

(f) H+ + OH– → H2O

1 [6]

M24. (a) (i) fertilisers

for 1 mark 1

(ii) 7 for 1 mark

1

(iii) 5 for 1 mark (ignore other units)

1

(b) (i) both nitrogen and hydrogen for 1 mark

1

(ii) two of: nitrogen; hydrogen/methane/natural gas; oxygen/air; water; any fuel (allow symbols, do not allow nitrogen oxides)

any two for 1 mark each 2

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(c) (i) alkali/alkaline/base/basic for 1 mark

1

(ii) must be nitrate for 1 mark

1

(iii) thermometer or any other temperature measuring device for 1 mark

1 [9]

M25. (a) (i) iron must be named

do not accept Fe 1

(ii) hydrogen 1

and oxygen mixtures 1

burn rapidly 1

(b) (i) lowers concentration accept dilutes the acid do not accept cooling

1

less collisions (between particles) 1

(ii) H+ (aq)

accept H3O+ only if 2 in front of H

2O

1

OH− (aq)

if spectator ions correctly included on both sides, maximum = 1 mark

1

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(iii) Ca(OH2) weak alkali

accept NaOH strong alkali 1

Ca(OH)2 causes no problems

accept NaOH causes named problem (eg caustic or exothermic or burns or corrosive)

1 [10]

M26. (a) (i) (s) (aq) (1) (g)

2 or 3 correct 1 mark 1 correct 0 marks

2

(ii) calcium chloride 1

(b) (i) points deduct 1 mark for each error to a maximum of 2 marks

2

line accept a single line ‘best fit’ curve accept reasonable attempt at curve

1

(ii) increase temperature or heat

accept increase surface area or increase concentration or description

1

(iii) 75% or ¾ not pure 1 mark

only 60 cm3 (instead of 80 cm3 of gas)

or × 100 1 mark 3

[10]

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M27. (a) (i) H2SO

4 or red (acidic) pH < 7

accept names of compounds accept correct use of acidic

1

NaOH or purple (alkaline) pH > 7

alkaline and neutral without any mention of pH for 1 mark only 1

NaCl or green (neutral) pH 7

ignore high or low pH 1

(ii) hydrogen (ion) accept proton accept hydroxonium ion

1

H+

accept H3O+ for hydroxonium ion

1

(b) (i) neutralisation 1

(ii) NaOH + HCl ignore state symbols

1

NaCl + H2O

ignore state symbols maximum of 1 mark if incorrectly balanced

1

(c) (i) sodium – 2 . 8 . 1 accept 2.8.1 written

1

chlorine – 2 . 8 . 7 accept 2.8.7 written

1

(ii) ion(s) 1

(iii) attraction between oppositely charged particles (ions) accept attraction between + and – particles (ions) accept electrostatic attraction

1

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(d) chloride ions lose electrons to form chlorine

Cl– – e– → Cl 1

hydrogen ions gain electrons to form hydrogen

H+ + e– → H

1

sodium hydroxide remains in solution

Na + and OH– remain in solution to form sodium hydroxide

1 [15]

M28. (a) (i) test: limewater

accept calcium hydroxide solution 1

result: ‘goes’ cloudy accept white or milky do not accept misty or chalky test must be correct before result mark can be considered

1

(ii) 2 NaHCO3 + H

2SO

4 →

Na2SO

4 + (2) H

2O + (2) CO

2

1

correctly balanced 1

(b) (i) H+ + OH–

1

→ H2O

deduct one mark if incorrectly balanced

accept H3O+ instead of H+ then 2H

2O needed for balance

1

(ii) pH increases accept numerical indication

1

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(c) addition of sulphuric acid 1

correct use of an indicator accept idea of forming a neutral solution

1

crystallisation (of neutral solution) accept description using evaporation

1 [10]

M29. (a) breakdown / decomposition / splits into elements /

not ions

separates into elements / produce a chemical reaction 1

using electricity 1

(b) lead bromide melted / free ions

not electrolyte 1

(c) (+) bromine element must be appropriate to electrode

1

(–) lead element must be appropriate to electrode

1

(d) fume cupboard / protective clothing allow safety glasses not safety mat

1 [6]

M30. (i) Mg + (H2SO

4) →

1

MgSO4 + 1

H2

deduct 1 mark if not balanced only if all three correct accept alternative metal of similar reactivity for example Zn or Fe candidate would not then be awarded first mark for Mg then error carried forward deduct 1 mark if not balanced only if all three correct

1

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(ii) to remove the (excess) magnesium accept separate accept insoluble substances or solids or residue do not accept unreactive substances or impurities or remove magnesium from sulphuric acid

1

(iii) to evaporate (some of the water or solution) 1

to form crystals or crystallise

accept to form a saturated solution or concentrated solution do not accept to leave MgSO

4

1 [6]

M31. (a) (i)

accept CaO3 → CaO + CO

2

1

calcium carbonate

→ calcium oxide

+ carbon dioxide

(ii) (thermal) decomposition accept endothermic accept reversible

1

(b) (i) neutralisation accept exothermic

1

(ii) sulphuric (acid) H2SO

4

2

(c) (i) to speed up the reaction accept to increase the rate of reaction or to increase the number or rate of collisions do not accept “dissolves” copper oxide faster

1

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(ii) all acid reacts accept there will be no acid left or acid used up

1

acid is neutralised (for 2 marks)

do not accept to form a concentrated or saturated solution 1

(excess) copper oxide collects in filter paper accept larger particles (of copper oxide) cannot pass through filter paper

1

copper sulphate solution passes through the filter paper accept dissolved copper sulphate passes through filter paper or smaller particles (of copper sulphate) in solution (liquid) pass through filter paper accept (black) solid collects in filter paper and filtrate or soluble solid or (blue) solution (liquid) passes through filter paper for 1 mark only

1 [10]

M32. (a) (i) to remove or separate copper oxide

accept to remove or separate unreacted or excess base accept to remove or separate insoluble solids

1

(ii) heat (the solution) accept heat the water accept evaporate the water rapid cooling/cool to lower temperature accept boil the water or solution not increase surface area, put in draught not increase the temperature

1

(iii) aqueous accept in water accept solution not soluble in water

1

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(b) add water/liquid/solution 1

colour changes to blue 1

[5]

M33. hydrogen ions (from acid) or protons / H+

1

react with hydroxide ions (from alkali) / OH1

to produce water

H + OH H2O gains all 3 marks

ignore state symbols molecules of hydrogen ions and molecules of hydroxide ions produce water = 2 marks if they fail to get any of the above marks they can get 1 mark for neutralisation / product neutral

1 [3]

M34. (i) to make sure all sulphuric acid reacts or to neutralise the acid or unreacted sulphuric acid difficult to remove owtte

ignore ‘to maximise the product’ accept otherwise (sulphuric) acid left

1

(ii) filter(ing) / filtration or described owtte accept use filter paper accept centrifuge and decant do not accept sieve / strain filter funnel is insufficient

1

(iii) no more solid / solute can dissolve

or maximum amount of solid owtte 1

at that temperature accept any link to temperature or any specified temperature

1

(iv) solubility decreases (as temperature falls) owtte accept less soluble in cold water answer must be linked to solubility ignore the extra cannot dissolve

1

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(v) otherwise get anhydrous CuSO4

accept otherwise get white CuSO4

accept do not get hydrated CuSO4

accept could get CuO or thermal decomposition / decomposes allow SO

3 / SO

2 produced

allow dehydration accept removes the water of crystallisation not just remove water from the crystals or just steam

1 [6]

M35. (a) (i) water

accept H2O

accept correct ringed answer in box 1

(ii) neutralisation accept underlining or any indication, eg tick

1

(b) sodium hydroxide 1

sulphuric acid apply list principletotal

1 [4]

M36. (a) all lead nitrate reacted or no lead nitrate left or enough KI to react with lead nitrate or to remove all the lead ions or to get maximum amount of I

2

ignore comments about speed do not accept to remove all the lead

1

(b) precipitate allow phonetic spelling do not accept ppt

1 1

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(c) filter / filtration / centrifuge / decant do not accept sieve

(d) any one from:

• removes (soluble) impurities

• removes (unreacted) KI

• removes KNO3

• removes (excess) solution

• removes nitrates purifying is insufficient do not accept removes potassium do not accept removes iodide

1

(e) answer based on filter paper, desiccator, suitable solvent (gentle) heat, drying cabinet, oven etc.

Accept any method of heating i.e. bunsen / hairdryer etc. Accept leave to evaporate / stand or leave in a warm room

e.g. place between dry filter paper, allow to dry e.g. use propanone, allow to dry e.g. leave on sunny window sill e.g. leave in a draught

the answer leave / evaporate / draught alone is insufficient

1

(f) wear gloves / mask or fume-cupboard or wash hands afterwards

ignore goggles / labcoat or extractor fan / do not touch etc. 1

[6]

M37. nitric acid 1

potassium hydroxide 1

water 1

[3]

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M38. (a) H+(aq) + OH– (aq) → H2O(l) or

H3O+(aq) + OH–(aq) → H

2O(l)

mark for correct equation mark for state symbols any other symbols = 0 marks accept correct spectator ions e.g. Na+(aq) + OH– (aq) + H+(aq) + Cl– (aq) → Na+(aq) + Cl– (aq)

+ H2O(l)

2

(b) (i) nitric acid and ammonia (solution) HNO

3 NH

3 / NH

4OH

mark for both accept ammonium hydroxide / NH

4OH instead of ammonia

do not accept ammonia hydroxide do not accept hydrogen nitrate solution accept correct formulae

1

(ii) provides oxygen or oxidising (agent) or oxidant

do not accept it contains oxygen alone or rich in oxygen

1 [4]

M39. (i) potassium hydroxide

accept correct formulae 1

water 1

(ii) fertiliser 1

(iii) H+

accept hydrogen but not H 1

[4]

M40. (a) (i) sulfuric

accept H2SO

4

accept sulphuric allow phonetic spellings

1

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(ii) CuO + H2SO

4 → CuSO

4 + H

2O

1 mark for reactants 1 mark for products ignore state symbols max 1 mark for incorrect balancing

2

(b) any two from:

• particles gain energy or particles have more energy

allow have more activation energy

• particles move faster allow they collide faster / quicker ignore move / vibrate more

• collide more often allow more collisions

• collide more energetically

• more of the collisions are successful or more particles have the activation energy

NB more successful collisions alone = 1 mark if particles are identified as electrons = max 1 mark

2 [5]

M41. (a) (i) (phosphoric) acid

allow phosphoric acid 1

(ii) hydrogen 1

(b) (i) faster / quicker / speeds it up (owtte) allow answers based on activation energy ignore helps it to react

1

(ii) most of the starting materials end up as useful products 1

(iii) H2O

allow HOH or OH2

1 [5]

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M42. (a) Compound A

any one from:

accept correct formulae

• sodium bromide

• potassium bromide

• ammonium bromide

• hydrogen bromide

• any metal bromide except silver and lead. 1

Compound B

silver nitrate accept silver sulphate

1

(b) the silver compound will decompose / silver ions be reduced to silver (owtte) accept film would darken owtte accept any idea of light changing silver bromide / silver ions / silver nitrate / silver sulphate allow ‘forms a black solid’ / it would turn black

1

(c) precipitation accept descriptions of precipitation reactions accept double decomposition accept precipitate do not allow displacement

1

(d) electrons 1

are gained the second mark must be linked to electrons accept it / silver / silver ions gains electrons for both marks ignore references to oxygen

1 [6]

M43. (a) 2Mg + O2 → 2MgO

accept correct multiples / fractions 1

of 95

(b)

electrons do not need to be paired accept dots / circles / e instead of crosses do not allow 2.6 without diagram

1

(c)

electrons do not need to be paired allow without bracket s/ must have the charge accept dots / circles / e instead of crosses ignore extra empty outer shells ignore nucleus

do not allow [2.8]2+ without diagram

1

(d) oppositely charged (ions / atoms) allow positive and negative(ions / atoms)

1

(they) attract must be in correct context accept held by electrostatic forces ignore ionic bonding maximum 1 if they refer to intermolecular forces / attractions / covalent bonds

1

(e) magnesium chloride accept MgCl

2 (if correctly written)

1 [6]

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M44. (a) gives out (heat) 1

(b) D 1

(c) L 1

(d) magnesium chloride 1

[4]

M45. (a) (i) any one from:

• they are positive / cations

• they are H+

• opposite charges attract ignore atom

1

(ii) potassium is more reactive (or reverse) assume ‘it’ refers to hydrogen allow potassium reacts with water allow potassium is very reactive or most reactive metal / element allow hydrogen gains electrons more easily / is reduced more easily accept potassium is higher up the reactivity series

1

(b) 6 and 2

accept correct multiples and fractions 1

(c) (i) the reaction / it is reversible or a description of a reversible reaction

allow ‘it is an equilibrium’ allow reversible symbol drawn correctly allow ‘the reverse / back reaction’

1

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(ii) lithium nitride

assume that ‘it’ or if they do not specify means lithium nitride

assume lithium / lithium nitrate refers to lithium nitride

• hydrogen is bonded / held / absorbed / has formed a compound / reacted with lithium nitride

1

plus one of:

• does not explode / cause a fire

• is not free / less hydrogen

• is not under pressure

• does not leak

• is only released slowly 1

• compound of hydrogen with lithium nitride / product is (more) stable / less reactive / less chance of a reaction accept converse for hydrogen as below assume that gas / hydrogen means gas in the cylinder • hydrogen (in cylinder) / gas is not bonded / held absorbed / in a compound / reacted with lithium nitride

1

plus one of: • can explode / cause a fire • is free • is under pressure • can leak • releases quickly

1

(d) (i) loss of an electron or loses electrons

do not accept any ref. to oxygen 1

(ii) full outer shell of 8 electrons on circle need not be paired can be ×, dot or e do not accept if extra electrons added to inner shell

1 [10]

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M46. (a) water / H2O / hydrogen oxide

1

(b) eg H (atom) loses an electron to form H+

or only a proton left 1

(c) is partially ionised in water 1

(d) (i) eg same concentration / quantity of Mg accept: volume of acid / ribbon for both / same time accept: volume of gas measured under the same conditions

1

(ii) C A D B 1

(e) (i) OH–

1

(ii) acidic 1

[7]

M47. (a) one nitrogen atom joined to three hydrogen atoms 1

correct pairs of electrons 1

(b) because ammonia is made of small molecules / simple molecules / simple molecular structures

1

and so there are weak forces between the molecules or and so the intermolecular forces are weak

1

incomplete answers that link only size of molecule or strength of intermolecular forces with boiling point only gain 1 mark

(c) (i) hydroxide 1

(ii) nitric 1

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(d) because this is an endothermic reaction 1

that takes in energy from the surroundings as the ammonium nitrate dissolves

1 [8]

M48. (a) 3

accept correct multiples 1

(b) sodium hydroxide / potassium hydroxide / alkali / a hydroxide 1

(c) the chromium ions form a precipitate which can be removed by filtration accept the chromium ions form a solid which can be removed by filtration

1 [3]

M49. Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response.

No relevant content. 0 marks

There is a brief description of the method or a risk assessment. Level 1 (1–2 marks)

There is some description of the method that may include a risk assessment.

Level 2 (3–4 marks)

There is a clear, balanced and detailed description of the method and a risk assessment.

Level 3 (5–6 marks)

of 95

examples of the chemistry points made in the response

The underlined words are needed to gain each bullet point.

• sulfuric acid is heated in a beaker and copper oxide is added with stirring

• until the copper oxide is in excess

• the mixture is filtered or the mixture is poured through a funnel and filter paper

• to remove the excess copper oxide

• some of the solution is evaporated or heated in an evaporating basin/dish

• the solution is allowed to crystallise / cool down

examples of the risk assessment points made in the response

• wear safety goggles – to protect eyes because sulfuric acid is corrosive / an irritant

• care when heating – to protect against burns

• wash hands after the preparation – copper sulfate is harmful

• care when handling glass apparatus – to protect against cuts [6]

M50. (a) a solid / insoluble salt is formed

accept salt / substance that does not dissolve forms 1

(b) hydroxide 1

(c) filtration 1

(d) risk is that chromium ions are toxic or harmful 1

[4]

M51. (a) 4 1

(b) A 1

of 95

(c) it is alkaline accept alkali / basic / base

1

(d) (i) salt 1

(ii) nitric 1

(ii) fertiliser 1

(e) because energy 1

is taken in (from the surroundings) second mark must be linked to energy

1 [8]

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