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Section A[60 marks]

Answerall questions in this section.

The time suggested to complete Section A is 90 minutes.

1 Figure 1 shows the set-up of apparatus for an experiment to determine the empirical

formula of magnesium oxide.

FIGURE 1

Results:

Mass of crucible + lid = 24.0 g

Mass of crucible + lid + magnesium = 26.4 g

Mass of crucible + lid + magnesium oxide = 28.0 g

(a) What is meant by empirical formula?

.

[1 mark]

(b) Based on the above results,

(i) Calculate the mass of magnesium and the mass of oxygen that have

reacted.

[1 mark]

(ii) Calculate the mole ratio of magnesium atoms to oxygen atoms.

[Relative Atomic Mass: O, 16; Mg, 24]

[1 mark]

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iii. determine the empirical formula of magnesium oxide

[1 mark]

(iv) write the chemical equation for the reaction in the experiment.

[1 mark]

(c) Why was the crucible lid opened once in a while during the experiment?

.

[1 mark]

(d) Metal X is placed below hydrogen in the reactivity series. You are required

to carry out an experiment to determine the empirical formula of the oxide

of metal X. The apparatus provided are combustion tube, glass tube, cork,

Bunsen burner, and porcelain dish.

(i) Draw a labeled diagram of the set-up of the apparatus for theexperiment.

[2 marks]

(ii) Describe the steps that should be taken to ensure that all the air in the

combustion tube has been expelled.

..

..

..

[3 marks]

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2 Figure 2 shows part of the Periodic Table of Elements.

1 18

H 2 13 14 15 16 17

Mg3 4 5 6 7 8 9 10 11 12

Fe

Figure 2

Based on Figure 2, answer the following questions.

(a) What is the element represented by the symbol Fe?

.[1 mark]

(b) In Figure 2, markX in the boxes for all the transition elements.

[1 mark]

(c) State one specific characteristic of transition elements.

.

[1 mark]

(d) Write the electron configuration for the Mg atom.

.

[1 mark]

(e) (i) Write the chemical equation for the reaction between aluminium and

oxygen gas.

..

[1 mark]

(ii) Briefly state the electron transfer in the bond formation between

aluminium and oxygen.

..

..

[2marks]

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Helium Gas

Light Not reactive colourless

Hydrogen gas

Light Flammable colourless

(f) Based on the above information, which gas is more suitable to be used in

meteorological balloons?

Give one reason.

.

[2 marks]

3 Figure 3 shows the flow chart for the industrial manufacture of sulphuric acid and theproduction of fertilizer Z

Figure 3

Based on Figure 3, answer the following questions,

(a) Name the process of manufacturing sulphuric acid.

.

[1 mark]

(b) Name the substance X.

.

[1 mark]

(c) Substance X could react directly with water to form sulphuric acid. Explain

why this step is not carried out in the industrial process.

.

[1 mark]

(d) Write the chemical equation when oleum reacts with water to form sulphuric

acid.

.[1 mark]

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(e) Name the substance Y and the fertilizer Z.

Substance Y :

Fertilizer Z : [2 marks]

(f) Write a chemical equation when sulphur dioxide reacts with water.

.

[1 mark]

4 Figure 4 shows the set-up of apparatus for the preparation of ethyl ethanoate from

the reaction of ethanol with ethanoic acid.

Figure 4

(a) On the Liebig condenser in Figure 4, mark "X' to indicate the place where

water flows in and Y where water flows out.

[1 mark]

(b) Why is the mixture heated using water bath?

.

.

[2 marks]

(c) (i) Name the reaction for the preparation of ethyl ethanoate.

..[1 mark]

The combustion of petrol in the engines of

vehicles produces sulphur dioxide. This gas

when dissolved in rain is corrosive.

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(ii) Write the chemical equation for the reaction in (c)(i).

..

[1 mark]

(d) The experiment is repeated by replacing ethanol with propanol

(i) Name the ester formed.

..

[1 mark]

(ii) State one physical property of the ester.

..

[1 mark]

(e) The flow chart below shows the conversion of ethanol to ethene and ethanol

to ethanoic acid.

EtheneProcess I

EthanolProcess II

Ethanoic Acid

Based on the flow chart, write the chemical equation for

(i) Process I.

[1 mark]

(ii) Process II.

[1 mark]

(f) An alkane has a structural formula as shown below.

What is the name of the alkane?

.

[1 mark]

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5 Figure 5 shows the set-up of apparatus to investigate the reactions that take place in

test tubes P and Q.

FIGURE 5

(a) State the observation for the reaction

(i) in test tube P.

..

[1 mark]

(ii) in test tube Q.

..

[1 mark]

(b) Write the ionic equation for the reaction in (a)(i).

.

[1 mark]

(c) State what is meant by oxidizing agent in terms of electron transfer.

.

[1 mark]

(d) Referring to the reaction that takes place in test tube P.(i) what is the change in the oxidation number of magnesium?

..

[1 mark]

(ii) name the oxidizing agent.

..

[1 mark]

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(e) Referring to the reaction that takes place in test tube Q,

(i) state the type of reaction that occurs.

..

[1 mark]

(ii) state the oxidation number of bromine in bromine water.

..

[1 mark]

(iii) what is the function of bromine water?

..

[1 mark]

(iv) name another reagent that can replace bromine water.

..

[1 mark]

6 A student carried out an experiment to determine the heat of displacement for the

reaction between copper and silver nitrate solution. In this experiment, excess

copper powder was added to 100 cm3 of silver nitrate solution 0.5 mol dm -3. The heat

of displacement in this experiment was - 05 kJ mol-3

.[Specific heat capacity of the solution is 4.2 J g-1 oC-1, and the density of the solution is 1

g cm -3]

(a) What is meant by heat of displacement?

.

[1 mark]

(b) Besides the data given above, state one other piece of data that is needed to

calculate the heat of displacement.

.[1 mark]

(c) State one precaution that must be taken while carrying out the experiment.

.

[1 mark]

(d) (i) State one observation of the experiment.

..

[1 mark]

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(ii) State the reason for the observation in (d)(i).

..

[1 mark]

(e) Based on the information from this experiment, calculate

(i) the number of moles of silver ions reacted.

[1 mark]

(ii) the amount of heat released.

[1 mark]

(iii) the change in temperature.

[1 mark]

(f) Draw an energy level diagram for the reaction in this experiment.

[2 marks]

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(g) The experiment is repeated using 100 cm3 of 1.0 mol dm-3 silver nitrate solution

and excess copper powder.

Calculate the temperature change in this experiment.

Explain why this change of temperature is different from that in (e)(iii).

.

.

[3 marks]

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Section B[20 marks]

Answer any one question from this section.

The time suggested to complete Section B is 30 minutes.

1 The rate of reaction is affected by several factors. One of the factors is the size of

particles.

(a) Explain the above statement based on the size of the particles. [2 marks]

(b) A student carried out three experiments to investigate the effects of the factors

influencing the rate of reaction. Table I shows the results of the experiments.

Experiment I II III

Set up ofapparatus

Temperature

/oC 30 40 50Time taken

for allmagnesiumto dissolve

/sec

50 20 15

Table 1

(i) Write the chemical equation for the reaction between magnesium and

hydrochloric acid. Calculate the maximum volume of hydrogen gas

produced.

[Relative atomic mass: Mg, 24; molar gas volume: 24 dm 3 mol-1 at

room condition] [4 marks]

(ii) Sketch the graphs for the volume of hydrogen gas against time for

Experiment I, II,and III on the same axes. [3 marks]

(iii) Calculate the average rate of reaction for Experiment I, II, and III in

cm3 s-1 [3 marks]

(iv) Compare the rates of reaction between Experiment I and Experiment II,

and between Experiment II and Experiment III.

With reference to collision theory, explain why there are differencesin the rates of reaction in the experiments. [8marks]

One kilogramme of meat, cut into big pieces, takes a

longer time to cook compared to one kilogramme of

meat cut into small pieces

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2 (a) State two methods of food preservation which are used in our daily lives and

explain how the methods work. [4 marks]

(b) A student discovered that his socks have oily stains. He washed them with

soap.Explain the cleansing action of soap on the oily stains. [8 marks]

(c) A student carried out fourexperiments to investigate the cleansing effects of

soap anddetergent on oily stains in soft water and hard water.

Table 2 shows the set-up of apparatus, types of water used, and the

observations for Experiments I, II, III, and IV.

Experiment I II III IV

Set up ofapparatus

observationOily stainsdisappeared

Oily stainsremains

Oily stainsdisappeared

Oily stainsdisappeared

Table 2

Compare the cleansing effects between (i) Experiments I and II (ii)

Experiments II and IV

Explain why there are differences in the observations: State the

substance which is more

suitable as a cleansing agent to remove oily stains. [8 marks]

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Section C[20 marks]

Answer any one question from this section.

The time suggested to complete Section C is 30 minutes.

3 (a) Lime juice was electrolysed using carbon electrodes.

What is produced at the cathode? Write a half-equation for the reaction.

[2 marks]

(b) Figure 6 shows two types of cell.

Figure 6

Compare and contrast cell P and cell Q. Include in your answer the

observation and half- equations for the reactions of the electrodes in bothcells. [8 marks]

(c) A student intends to electroplate an iron key with a suitable metal to

beautify it. Design a laboratory experiment to electroplate the iron key.

Your answer should consist of the following:

Chemicals requiredProcedures of the experimentDiagram showing the set-up of apparatusChemical equation involved in the reactionObservation

[10 marks]

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4 (a) A farmer discovered that his vegetables were not growing well because the

soil was poor and acidic. As a chemistry student, you can help the farmer.

Suggest how the farmer can overcome the problem. [2marks]

(b) Figure 7 shows an incomplete flow chart of cation and anion tests for saltX.

Use the reagents listed below and complete the flow chart to confirm thatsalt X contains Pb2+ ions and C03

2- ions. Include your observations.

[8 marks]

(c) You are required to prepare dry magnesium chloride salt. The chemicals

supplied are

magnesium sulphate solutions, dilute hydrochloric acid, potasium carbonate solution.

Describe a laboratory experiment to prepare the salt. In your description,

include the chemical equations involved. [10 marks]

REAGENTS

Dilute hydrochloric acid, dilute

nitric acid, and lime water