C5 Revision cards

C5 Revision Questions

C5 Revision cards

Question 1

• What is a mole of a substance?

.... of 50

C5 Revision cards

Answer 1

• A mole is 6.02 x 1023 (Avogadro’s number) of particles of a substance, the same number of particles in 12g of Carbon-12.

.... of 50

C5 Revision cards

Question 2

• How do you calculate molar mass?

.... of 50

C5 Revision cards

Answer 2

• Molar mass is calculated by adding up all the relative atomic masses in the formula.

.... of 50

C5 Revision cards

Question 3

• What is the relative atomic mass of an element?

.... of 50

C5 Revision cards

Answer 3

• The relative atomic mass of an element is the average mass of the element compared to the mass of one atom of Carbon-12.

.... of 50

C5 Revision cards

Question 4

• How do we calculate the number of moles of a substance (solid)?

.... of 50

C5 Revision cards

Answer 4

• Number of moles (solid) = mass of chemical

Molar mass

.... of 50

C5 Revision cards

Question 5

• What does conservation of mass mean?

.... of 50

C5 Revision cards

Answer 5

• Conservation of mass means that in a chemical reaction, the mass of the atoms at the start equals the mass of the atoms at the finish.

.... of 50

C5 Revision cards

Question 6

• What is the general word equation for the thermal decomposition of a metal carbonate?

.... of 50

C5 Revision cards

Answer 6

• Metal carbonate metal oxide + carbon dioxide

.... of 50

C5 Revision cards

Question 7

• What is empirical formula?

.... of 50

C5 Revision cards

Answer 7

• Empirical formula is the simplest way of writing a whole-number ratio of each type of atom inside a molecule.

.... of 50

C5 Revision cards

Question 8

• How is percentage mass calculated?

.... of 50

C5 Revision cards

Answer 8

% mass of element = total mass of the element in the compound x100

Relative formula mass of the compound

.... of 50

C5 Revision cards

Question 9

• What is the concentration of a solution?

.... of 50

C5 Revision cards

Answer 9

• Concentration is the amount of solute (solid) in grams dissolved in 1dm3 of solution.

.... of 50

C5 Revision cards

Question 10

• What are the units of concentration?

.... of 50

C5 Revision cards

Answer 10

• The units of concentration are mol/dm3 or g/dm3

.... of 50

C5 Revision cards

Question 11

• What is volume measured in?

.... of 50

C5 Revision cards

Answer 11

• Volume is measured in cm3 or dm3

.... of 50

C5 Revision cards

Question 12

• How do you calculate the number of moles of a solution?

.... of 50

C5 Revision cards

Answer 12

• Amount in moles (solution) = concentration x volume in dm3

OR

• Amount in moles (solution) = concentration x volume in cm3

1000

n = c x v/1000

.... of 50

C5 Revision cards

Question 13

• How many cm3 are in 1 dm3?

.... of 50

C5 Revision cards

Answer 13

• There are 1000 cm3 in 1 dm3

.... of 50

C5 Revision cards

Question 14

• What is the general word equation for the reaction between acids and alkalis?

.... of 50

C5 Revision cards

Answer 14

• Acid + alkali salt + water

.... of 50

C5 Revision cards

Question 15

• What pH is an acid?

.... of 50

C5 Revision cards

Answer 15

• Acids have a pH less than 7

.... of 50

C5 Revision cards

Question 16

• What pH is a neutral solution?

.... of 50

C5 Revision cards

Answer 16

• A neutral solution is pH 7

.... of 50

C5 Revision cards

Question 17

• What pH is an alkali?

.... of 50

C5 Revision cards

Answer 17

• Alkalis have a pH of more than pH7

.... of 50

C5 Revision cards

Question 18

• What colour is litmus in alkali?

.... of 50

C5 Revision cards

Answer 18

• Litmus is blue in alkali

.... of 50

C5 Revision cards

Question 19

• What colour is litmus in acid?

.... of 50

C5 Revision cards

Answer 19

• Litmus is red in acid.

.... of 50

C5 Revision cards

Question 20

• What colour is phenolphthalein in alkali and in acid?

.... of 50

C5 Revision cards

Answer 20

• Phenolphthalein is pink in alkali, colourless in acid

.... of 50

C5 Revision cards

Question 21

• How do you calculate the number of moles of gas produced in a reaction?

.... of 50

C5 Revision cards

Answer 21

• Number of moles of gas = volume of gas in dm3

24

.... of 50

C5 Revision cards

Question 22

• What is the limiting reactant in a chemical reaction?

.... of 50

C5 Revision cards

Answer 22

• The reactant used up first is the limiting reactant.

.... of 50

C5 Revision cards

Question 23

• On a graph, what shows the rate of reaction?

.... of 50

C5 Revision cards

Answer 23

• The gradient of a graph shows the rate of the reaction.

.... of 50

C5 Revision cards

Question 24

• What is the word and symbol equation for the reaction to form ammonia?

.... of 50

C5 Revision cards

Answer 24

• Nitrogen + Hydrogen ⇌ ammonia

• N2(g) + 3H2 (g) ⇌ 2NH3(g)

.... of 50

C5 Revision cards

Question 25

• What does this symbol mean ⇌?

.... of 50

C5 Revision cards

Answer 25

• The ⇌ symbol means that a reaction is reversible.

.... of 50

C5 Revision cards

Question 26

• When is a system in dynamic equilibrium?

.... of 50

C5 Revision cards

Answer 26

• A chemical system is in dynamic equilibrium when:

– Concentration of reactants and products remain the same

– Rate of forward reaction = rate of reverse reaction

– Closed system

.... of 50

C5 Revision cards

Question 27

• What factors can affect the position of equilibrium composition?

.... of 50

C5 Revision cards

Answer 27

Things that can affect the position of equilibrium:

• Concentrations of reactants or products

• Pressure in reactions involving gases

• Temperature

.... of 50

C5 Revision cards

Question 28

• If the temperature of an exothermic reaction is increased, what happens to the position of equilibrium?

.... of 50

C5 Revision cards

Answer 28

• If the temperature of an exothermic reaction is increased, the equilibrium moves to the left, making more reactants.

.... of 50

C5 Revision cards

Question 29

• What is Le Chatelier’s principle?

.... of 50

C5 Revision cards

Answer 29

Le Chatelier’s principle states:

• When a system in dynamic equilibrium is subjected to change, the position of equilibrium will shift to minimise the change.

.... of 50

C5 Revision cards

Question 30

• What are the symbol equations for the three stages of the contact process?

.... of 50

C5 Revision cards

Answer 30

The three stages of the contact process:

1. S + O2SO2

2. 2SO2 + O2 ⇌ 2SO3

3. SO3 + H2O H2SO4

.... of 50

C5 Revision cards

Question 31

• What is the contact process?

.... of 50

C5 Revision cards

Answer 31

• The Contact process is used to make sulfuricacid.

.... of 50

C5 Revision cards

Question 32

• What is sulfuric acid used to make?

.... of 50

C5 Revision cards

Answer 32

• Sulfuric acid is used to make fertilisers, paint, plastics and soap.

.... of 50

C5 Revision cards

Question 33

• What are the three raw materials used for making sulfuric acid?

.... of 50

C5 Revision cards

Answer 33

• The three raw materials for making sulfuricacid are sulfur, air and water

.... of 50

C5 Revision cards

Question 34

• What conditions are required for the contact process?

.... of 50

C5 Revision cards

Answer 34

The following conditions are used in the Contact process:

• V2O5 catalyst

• Temperature around 450°C

• atmospheric pressure.

.... of 50

C5 Revision cards

Question 35

• Do catalysts alter the position of equilibrium?

.... of 50

C5 Revision cards

Answer 35

• No, catalysts do not affect the position of equilibrium. They do make the reaction go faster, so equilibrium is achieved faster.

.... of 50

C5 Revision cards

Question 36

• What ion is responsible for all reactions of acids?

.... of 50

C5 Revision cards

Answer 36

• H+ ions are responsible for all reactions with acids.

• Acids are proton donors.

.... of 50

C5 Revision cards

Question 37

• What salts are made when sulfuric acid reacts with metal or metal compound?

.... of 50

C5 Revision cards

Answer 37

• Sulfates are the salts produced when sulfuricacid reacts with a metal or metal compound.

.... of 50

C5 Revision cards

Question 38

• What salts are formed when nitric acid reacts with a metal or metal compound?

.... of 50

C5 Revision cards

Answer 38

• Nitrates are the salts produced when nitric acid reacts with a metal or metal compound.

.... of 50

C5 Revision cards

Question 39

• What salts are formed when hydrochloric acid reacts with a metal or a metal compound?

.... of 50

C5 Revision cards

Answer 39

• Chlorides are the salts formed when hydrochloric acid reacts with a metal or metal compound.

.... of 50

C5 Revision cards

Question 40

• What happens when strong acids are added to water?

.... of 50

C5 Revision cards

Answer 40

• The acid releases H+ ions (protons) into solution when dissolved in water

– E.g. Hydrochloric acid, HCl

– HCl(g) + aqH+ (aq) + Cl-(aq)

Strong acids completely ionise in water.

.... of 50

C5 Revision cards

Question 41

• What happens to weak acids when dissolved in water?

.... of 50

C5 Revision cards

Answer 41

• When weak acids dissolve in water they only partially ionise.

• E.g.

• HA(aq) ⇌H+ (aq) + A- (aq)

• E.g. Ethanoic acid

• CH3COOH ⇌ H+ + CH3COO-

.... of 50

C5 Revision cards

Question 42

• What is the difference between a strong acid and a concentrated acid?

.... of 50

C5 Revision cards

Answer 42

• The strength of an acid is a measure of the degree of ionisation of the acid. A strong acid completely ionises.

• The concentration of an acid tells us how many moles of acid there are in a dm3 of solution. A concentrated acid has a high amount of moles of acid in a dm3 of solution.

.... of 50

C5 Revision cards

Question 43

• Is ethanoic acid or hydrochloric acid better at conducting electricity? Explain why.

.... of 50

C5 Revision cards

Answer 43

• Hydrochloric acid would conduct electricity better than ethanoic acid. Ethanoic acid has a lower concentration of H+ ions than the same concentration of hydrochloric acid. It is H+

ions that carry the charge so ethanoic acid is less conductive.

.... of 50

C5 Revision cards

Question 44

• What is the colour the precipitate formed when lead nitrate solution is added to the following halide ions?

• Cl-

• Br-

• I-

.... of 50

C5 Revision cards

Answer 44

• Cl- = white precipitate

• Br- = cream precipitate

• I- = bright yellow precipitate

.... of 50

C5 Revision cards

Question 45

• What ion is barium sulfate used to test for? What is the positive result for this test?

.... of 50

C5 Revision cards

Answer 45

• Barium chloride is used to test for sulfate ions.

• If sulfate ions are present, a white precipitate forms when barium chloride is added.

.... of 50

C5 Revision cards

Question 46

• Why do the reactants need to be soluble in a precipitation reaction?

.... of 50

C5 Revision cards

Answer 46

• In precipitation reactions, the reactants need to be able to move if they are to collide and react. This is why the reactants need to be soluble.

.... of 50

C5 Revision cards

Question 47

What are the state symbols for the following:

• Solid

• Liquid

• Gas

• Aqueous (dissolved in water)

.... of 50

C5 Revision cards

Answer 47

The state symbols for the following are:

• Solid (s)

• Liquid (l)

• Gas (g)

• Aqueous (dissolved in water) (aq)

.... of 50

C5 Revision cards

Question 48

• What are the four stages in preparing an insoluble salt?

.... of 50

C5 Revision cards

Answer 48

• To make an insoluble salt:

1. Mix the solutions of the reactants

2. Filter the precipitate

3. Wash the precipitate with distilled water

4. Dry the precipitate

.... of 50

C5 Revision cards

Question 49

• What are spectator ions?

.... of 50

C5 Revision cards

Answer 49

• Spectator ions do not directly take part in a reaction.

.... of 50

C5 Revision cards

Question 50

• What does an ionic equation show?

.... of 50

C5 Revision cards

Answer 50

• Ionic equations show only what is actually reacting, only the reacting ions are shown.

.... of 50