QUESTION 1:

PAGE

22

QUESTION 1:

A group of students carried out an experiment to investigate the effect of type of electrodes when aqueous copper(II) chloride solution is electrolyzed.The electrolysis was first carried out by using carbon electrodes.

Both the electrodes were weighed.

Copper(II) chloride solution was electrolyzed for 45 minutes.

Then both the carbon electrodes were weighed again.

The experiment was repeated by replacing carbon electrodes with copper electrodes.

Diagram 1.1 shows the set-up of apparatus used for the electrolysis of copper(II) chloride solution using carbon electrodes.

Beginning of the experimentAfter 45 minutes

Diagram 1.1Diagram 1.2 shows the set-up of apparatus for the electrolysis of copper(II) chloride solution using copper electrodes.

Beginning of the experiment

After 45 minutes

Diagram 1.2

(a)Write the observation and inference obtained at the carbon anode and both the copper electrodes during the electrolysis.

Type of electrodes

Observations Inference

Carbon anodeCopper anodeCopper cathode

[6 marks]

(b)Based on the experiment, state

(i)the manipulated variable.

..

(ii)the responding variable.

..

(iii)the constant variable.

..

[3 marks]

(c)State the hypothesis for the experiment.

[3 marks]

(d)Based on the experiment in Diagram 1.1, state the colour change of the copper(II) chloride solution after 45 minutes.

[3 marks]

(e)Classify all the ions present in copper(II) chloride solution into cations and anions.

[3 marks]

QUESTION 2

A student carried out an experiment to determine the end-point for the titration of 25.0 cm3 of

1.0 mol dm-3 sodium hydroxide solution with 1.0 mol dm-3 hydrochloric acid. Phenolphthalein is used as the acid-base indicator. Hydrochloric acid is added until the end-point of titration is reached.

Table 2 shows the three burette readings for the titrations that have been conducted.

Titration no.

I

II

III

Initial burette

reading

Final burette

reading

Table 2

(a)Record the burette readings for the three titrations in the spaces provided in Table 1.

[3 marks]

(b)Construct a table and record the initial burette reading, final burette reading and the volume of acid used for each titration.

[3 marks]

(c)Calculate the average volume of hydrochloric acid used in the experiment.

.

[3 marks]

(d)If the experiment is repeated by replacing 1.0 mol dm-3 of hydrochloric acid with

1.0 mol dm-3 of sulphuric acid, predict the volume of sulphuric acid needed to reach the end-point of titration.

.....

[3 marks]

(e)Give the operational definition for the end-point of titration.

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

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

[3 marks]

QUESTION 3

Diagram 3.1 shows the set-up of apparatus for an experiment to compare the reactivity of

alkali metals towards their reaction with oxygen.

Diagram 3.1The experiment is carried out using a small piece of lithium, potassium and sodium respectively to react with oxygen gas.

Observations on the alkali metals in the experiment are shown in Table 3.

Set

Set-up of apparatus

Observation

I

Lithium burns slowly and produces white fume.

II

III

Table 3(a) Look at the flame produced in each experiment in Table 3. Complete the Table 3 by stating the observation for each reaction of alkali metals towards oxygen.

[3 marks]

(b) Based on the experiment, complete the table below.

Manipulated variable:

____________________________

____________________________

____________________________

Method to manipulate the variable:

__________________________________________

__________________________________________

__________________________________________

Responding variable:

____________________________

____________________________

____________________________

How the variable is responding:

__________________________________________

__________________________________________

__________________________________________

Fixed variable:

____________________________

____________________________

____________________________

Method to maintain the fixed variable:

__________________________________________

__________________________________________

__________________________________________

[6 marks]

(c) State one hypothesis for the experiment.

[3 marks]

(d) Give one inference based on the results of the reaction between lithium and oxygen gas.

[3 marks]

(e) Based on the observation in Table 3, arrange lithium, potassium and sodium in descending order of reactivity towards oxygen.

[3 marks]

(f) The experiment is repeated using a small piece of rubidium to react with oxygen. Rubidium is more reactive than lithium, potassium and sodium.

Predict the observation for this experiment.

[3 marks]

(g) Diagram 3.2 shows the reading of pH meter when the metal oxides formed in Set I, II and III dissolved in water.

Set

SetSet-up of apparatus

Susunan radas

I

II

III

Diagram 3.2

(i) Record the pH value to one decimal place for Set I, Set II and Set III.

Set I : ..

Set II : ..

Set III : .

[3 marks]

(ii) Construct a table to record the pH value for Set I, Set II and Set III.

[3 marks]

(iii) State the operational definition for the alkali.

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

.

[3 marks]

(iv) The following is a list of chemical substances with pH value:

Chemical substance

pH value

Ammonia solution

11

Potassium hydroxide solution

14

Sodium hydroxide solution

13

Classify these substances into strong alkali and weak alkali.

[3 marks]

QUESTION 4

A student carried out three experiments to study the reaction of alkali metal with water.

.

Set up of experiment apparatusObservation of the alkali metal

(a) Complete the diagram by stating the observations for the reaction of group 1 metals with water

(b) After each experiment , a pH meter is dipped into the solution in the basin. The pH value of the solution is 13.

(c) Based on the observations in the experiment above, state the relationship between the position of the elements in Group 1 of the Periodic Table of Elements with the reactivity of the elements towards water.

..

..

..

5. An experiment is carried out to study the relationship between the concentration of hydrogen ions,H+ and the pH value of hydrochloric acid.

Diagram 5 shows the pH value of five solution of hydrochloric acid, a strong acid with different concentration.

(b) Construct a table and record the concentration of acid and the pH value for this experiment.

..

..

..

(c) Give the operational definition for the strong acid.

(d) State the variables involved in this experiment

Manipulated variable:...

Responding variable:...

Controlled variable:..

(e) State the hypothesis for this experiment.

(f) Classify the ions in hydrochloric acid solution into anion and cation.

(g) Calculate the number of moles of hydrogen ion in 50 cm3 of 0.01 mol dm-3 hydrochloric acid.

(h) Predict the pH value if the experiment is repeated by using 0.01 mol dm-3 of ethanoic acid.

..

..

..

QUESTION 5

The diagram 6 below shows the set-up apparatus of the experiment to investigate the effect of metal on rusting of iron, when it is in contact with other metals. Three iron nails coil with different metals are placed separately into three test tubes A, B and C, the test tube D as a control. Each of the test tubes is filled with a agar-agar solution containing a small amount of phenolphthalein and potassium hexacyanoferrate(III) solution. The apparatus is set aside for one day.

Table below shows the result of the experiment is set aside after 1 day.

Test tube

ABCD

Intensity of dark blue colour

NoneNoneVery highLow

Pink colouration

PresentPresentPresentPresent

Inference

(a) State the hypothesis for this experiment.

[ 3 marks](b) For this experiment, state:

(i) The manipulated variable

.. (ii) The responding variable

..

(iii) The constant variable

[3 marks]

(c) Based on the observations, complete the inferences in the table above.

[3 marks](d) Write half-equation in oxidation and reduction for the rusting of iron.

Oxidation : .[3 marks]

Reduction: ..

[3 marks](e) State the operational definition for the rusting of iron.

. [3 marks](f) State the function of potassium hexacyanoferrate(III) solution.

..

.

[3 marks](g) Explain why rusting of iron is the redox reaction.

... [3 marks](h) Explain why the present of pink colour all over the test tube..

.

. [3 marks]

(i) State the change of the oxidation number of iron occurs in test tube C. .

[ 3 marks] (j) Based on this experiment classify the metals can provide sacrificial protection and metals that cannot provide sacrificial protection to iron.

[3 marks](k) State three ways to control rusting of iron...

..

..

.. [3 marks]

QUESTION 6

Diagram 1.1 shows the set-up of apparatus for Experiment I, II, III, IV, V and VI to investigate the effect of temperature on the rate of reaction between sodium thiosulphate and sulphuric acid. 50 cm3 of 0.1 mol dm-3 of sodium thiosulphate solution is poured into a conical flask and is heated to 30C. 5 cm3 of 2 mol dm-3 of sulphuric acid is added immediately to the sodium thiosulphate solution. The conical flask is then placed on a paper with X as shown in Diagram 1.1. The time taken for the mark X to disappear from sight is recorded.

The experiment is repeated with sodium thiosulphate solutions at 40 oC, 50 oC, 55 oC, 60 oC and 65 oC.

Diagram 1.2 shows the readings of the stopwatch in each experiment.

(a) (i)Record the stopwatch readings in the space provided in Diagram 1.2.

[3 marks]

(ii)Calculate for each experiment. Construct a table to record and show all the data in the experiments. These data will be used to plot a graph in 1 (e).

[3 marks](b) State a hypothesis for this experiment.

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

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

[3 marks](c) State three conditions that must be kept constant in this experiment.

1.

2.

3.

[3 marks](d) State the operational definition of the rate of reaction based on this experiment.

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

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

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

[3 marks](e) Plot a graph of against temperature.

[3 marks](f) Based on the graph you have drawn, find the time taken for the mark X to disappear from sight if the temperature of the sodium thiosulphate solution is 45 oC.

[3 marks](g) If 50 cm3 of 0.05moldm-3 of sodium thiosulphate is used in Experiment I, predict the time taken for the mark X to disappear from sight. Explain your answer.

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

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

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

[3 marks](h) Food becomes stale more quickly when the weather is hot. Explain this observation.

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

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

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

[3 marks](i) In another experiment, the effect of concentration on the rate of reaction is studied. 50 cm3 of 0.08 mol dm-3 sodium thiosulphate solution is prepared from 0.1 mol dm-3 sodium thiosulphate solution. Calculate the volume of 0.1 mol dm-3 sodium thiosulphate solution used.

[3 marks](j) Describe how you would prepare the sodium thiosulphate solution in (i) accurately.

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

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

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

[3 marks]PLANNING FOR THE EXPERIMENT:

QUESTION 1

(a) Diagram 2(a) shows two sets, Set I and Set II, of the apparatus set-up and the results for an experiment to study the effects of metals X and Y on the rusting of iron.

SetApparatus set-upResult after 3 daysI

Iron nail did not rustII

Iron nail rustedDiagram 2(a)Referring to the information above, plan a laboratory experiment to investigate the effect of named metals X, Y and named electrolyte Z on the rusting of iron.

ANSWER:Problem statement:

How do/(Do) different type of metals / (metals X and Y) in contact with iron in the presence of an electrolyte affect rusting of iron ?

Variables:

Manipulated variable: metal X and metal Y // Different type of metals

Responding variable: the rusting of iron

Fixed variable: iron nail// electrolyte/(named) // agar/jelly solution //temperature

Hypothesis:

Metal Y causes iron nail rusting while metal X does not.// A more electropositive metal/(metal X) will prevent iron from rusting while a less electropositive metal (metal Y) will be rusting iron.

Materials:

Iron nails, magnesium strip, zinc strip, aluminium strip, tin strip ,copper strip, lead strip, silver strip, agar-agar solution + potassium hexacyanoferrate(III) solution+phenolphthalein indicator, any suitable electrolyte.Apparatus:

test-tubes, sand paperProcedure:

1. Clean iron nails, magnesium ribbon and copper strip with sand paper.

2. Coil the iron nails with magnesium ribbon and copper strip.

3. Place all the iron nails in separate test tubes.

4. Pour the hot agar containing potassium hexacyanoferrate(III) solution and phenolphthalein indicator into the test tubes.

5. Keep the test tubes in a test tube rack and leave them aside for 3 days.

6. Record your observations.

Tabulation of data:Set//Pair of metalsObservation

I//Mg-Fe

II//Cu-Fe

QUESTION 2

Referring to the above information, design a laboratory experiment to investigate the effect of the temperature of reactant on the rate of reaction.ANSWER:Aim

: To study the effect of temperature on the rate of reaction

Problem statement: How does temperature affect the rate of reaction?

Hypothesis:

The rate of reaction will increase if the temperature of reactants increases

Variables:

Manipulated: temperature

Responding: rate of reaction

Constant: volume and concentration of acid /

volume and concentration of sodium thiosulphate

Materials:

1 mol dm -3 sulphuric acid, 0.2 mol dm -3 sodium thiosulphate solution, white paper

Apparatus:

Conical flask, measuring cyclinder, stopwatch, Bunsen burner, wire gauze, tripod stand, thermometer.

Procedure:

1. An X is marked on a piece of white paper.

2. Using measuring cyclinder, 50 cm 3 of 0.2 mol dm -3 sodium thiosulphate solution is measured and poured into the conical flask which is the placed on the paper marked X.

3. The temperature of the sodium thiosulphate solution is recorded.

4. Using measuring cyclinder, 5 cm 3 of 1.0 mol dm -3 sulphuric acid is measured.

5. Immediately, the sulphuric acid is poured into the conical flask and shaken.

6. The stopwatch is started.

7. The formation of yellow precipitate of sulphur is on served at the top of the conical flask. Time is recorded when the X mark on the white paper is no longer visible.

8. The experiment is repeated. Each time the temperature of the sodium thiosulphate solution is increased by 5 0 C .

Tabulation of data:

Temperature of solution/ 0 C3035404550

Time / s

1/time ( s -1 )

QUESTION 3The equation represents the decomposition of hydrogen peroxide.

The rate of decomposition of hydrogen peroxide can be increased by adding manganese(IV) oxide powder which acts as a catalyst.

Plan a laboratory experiment to investigate the effect of catalyst on the decomposition of hydrogen peroxide. Answer:Aim

: To study the effect of the amount of catalyst on

the rate of reaction.

Problem statement: How does the amount of catalyst affect the rate of reaction?

Hypothesis:The decomposition rate of hydrogen peroxide will increase if the amount of manganese(IV) oxide increases.

Variables:

Manipulated: amount of catalyst

Responding: Rate of reaction

Constant: volume and concentration of hydrogen peroxide solution

Materials.

Hydrogen peroxide solution, manganese(IV) oxide, distilled water

Apparatus:

Conical flask, burette, basin, measuring cyclinder, stopwatch, retort

Procedures:

1. The burette and basin are filled with water.

2. The burette is inverted in the basin filled with water.

3. 50 cm 3 hydrogen peroxide solution is measured with the measuring cyclinder and poured into the conical flask.

4. A piece of manganese(IV) oxide is dropped into the hydrogen peroxide solution in the conical flask.

5. Immediately,the stopwatch is started.

6. The volume of oxygen gas released is recorded every 30 seconds until 5 minutes.

7. The experiment is repeated by adding 4 pieces of manganese(IV) oxide.

8. The volume and concentration of hydrogen peroxide solution used is the same.Tabulation of data:

Time/ s0306090120150180210240270300

Burette reading/ cm 3

Volume of gas / cm 3

Question:

Your planning must include the following items:

(a) Statement of the problem

[3 marks](b) All the variables

[3 marks](c) Hypothesis

[3 marks](d) List of materials and apparatus[3 marks](e) Procedure

[3 marks](f) Tabulation of data

[2 marks]

[ 17 marks ]

Copper(II) chloride solution (blue in colour)

Copper electrodes

A

A

Copper(II) chloride solution

Carbon electrodes

A

A

40

38

39

......

27

25

26

......

......

14

12

13

......

27

25

26

15

13

14

......

2

0

1

......

cm3

27

25

26

Oxygen gas

Gas jar

Alkali metal

White fumes

Lithium

White fumes

Potassium

White fumes

Sodium

pH value

13.19

pH meter

Litium hydroxide solution

pH value

13.61

pH meter

Potassium hydroxide solution

pH value

13.33

pH meter

Sodium hydroxide solution

Metal Y

Iron nail

Electrolyte Z

EMBED PBrush

Metal X

Iron nail

Electrolyte Z

EMBED PBrush

When sodium thiosulphate solution, Na2S2O3 reacts with dilute sulphuric acid, a yellow precipitate of sulphur is formed. The temperature of sodium thiosulphate affect the rate of reaction.

Hydrochloric acid

0.001 mol dm-3

Hydrochloric acid

0.0001 mol dm-3

3.0

4.0

Hydrochloric acid

0.1 mol dm-3

Hydrochloric acid

1.0 mol dm-3

Hydrochloric acid

0.01 mol dm-3

1.0

0.0

2.0

EMBED PBrush EMBED PBrush EMBED PBrush

pH value :_____ pH value :_____ pH value :_____

EMBED PBrush EMBED PBrush

pH value :_____ pH value :_____

Diagram 5

Record the reading of pH value for each of the solution in the spaces provided in Diagram 2.

Hiss

pop

hiss

Diagram 1.2

Iron nail

Iron nail

Iron nail

Magnesium strip

Zinc strip

Copper strip

Diagram 6

At 55 oC

.

At 65 oC

.

At 60 oC

.

Experiment IV

Experiment V

Experiment VI

At 30 oC

.

At 40 oC

.

At 50 oC

Experiment III

Experiment II

Experiment I

Diagram 1.1

Mark X

Sodium thiosulphate solution

+ sulphuric acid

2H2O2 ( 2H2O + O2

Iron nail

Eye

4541/3 BENGKEL AMBANG SPM 2009

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