CAIE IGCSE Chemistry Chemical Reactions Questions

Practise reaction types, rates, collision theory, catalysts, reversible reactions, equilibrium and industrial conditions across this CAIE IGCSE Chemistry unit.

Covered syllabus points

6.1 Physical and chemical changes 6.2 Rate of reaction 6.3 Reversible reactions and equilibrium 6.4 Redox

[Maximum number: 2]

Limestone rock is mainly calcium carbonate, $\mathrm{CaCO}_{3}$ .

(a)

The 'limestone cycle' is shown. Each step is numbered.

Figure for Question (a) — CAIE IGCSE Chemistry

[ 2 ]

(i)

Which step involves a physical change?

[ 1 ]

(ii)

Suggest how step 2 could be reversed.

[ 1 ]

[Maximum number: 5]

Some elements are shown in the order they appear in the reactivity series. The most reactive element is at the top.
> sodium calcium magnesium aluminium zinc iron hydrogen copper

(a)

When zinc granules are added to aqueous copper(II) sulfate, a reaction occurs. During the reaction, a red-pink solid is formed and the solution becomes colourless.

[ 5 ]

(i)

Explain, in terms of particles, why the rate of this reaction increases when the temperature is increased.

[ 3 ]

(ii)

Suggest two other ways of increasing the rate of this reaction.

1

2

[ 2 ]

[Maximum number: 9]

Sulfuric acid can be manufactured from the raw materials sulfur, air and water. The process can be divided into four stages.
stage 1 converting sulfur into sulfur dioxide
stage 2 converting sulfur dioxide into sulfur trioxide
stage 3 converting sulfur trioxide into oleum, $\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{7}$
stage 4 converting oleum into sulfuric acid
stage 1

(a)

Describe how sulfur is converted into sulfur dioxide.

[ 1 ]

(b)

Sulfur dioxide is converted into sulfur trioxide according to the following equation.

2 \mathrm{SO}_{2}+\mathrm{O}_{2} \rightleftharpoons 2 \mathrm{SO}_{3}

The reaction is carried out at a temperature of $450^{\circ} \mathrm{C}$ and a pressure of 1-2 atmospheres using a catalyst. The energy change, $\Delta H$ , for the reaction is $-196 \mathrm{~kJ} / \mathrm{mol}$ .

[ 8 ]

(i)

What is the meaning of the symbol ⇌?

[ 1 ]

(ii)

Name the catalyst used in this reaction.

[ 1 ]

(iii)

Why is a catalyst used?

[ 1 ]

(iv)

If a temperature higher than $450^{\circ} \mathrm{C}$ were used, what would happen to the amount of sulfur trioxide produced? Give a reason for your answer.

[ 2 ]

less $\mathrm{SO}_{3}$

forward reaction is exothermic/it is exothermic/reverse reaction is endothermic

(v)

Suggest a reason why a temperature lower than $450^{\circ} \mathrm{C}$ is not used.

[ 1 ]

(vi)

If a pressure higher than 1-2 atmospheres were used, what would happen to the amount of sulfur trioxide produced? Give a reason for your answer.
stage 3

[ 2 ]

more $\mathrm{SO}_{3}$

fewer moles or molecules (of gas) on right-hand side/ more moles or molecules(of gas) on left-hand side

[Maximum number: 3]

Sulfur is a Group VI element.

(a)

$\mathrm{Na}_{2} \mathrm{SO}_{3}$ is oxidised by acidified aqueous potassium manganate(VII).

[ 3 ]

(i)

State what VII refers to in the name potassium manganate(VII).

[ 1 ]

(ii)

State the colour change when this reaction happens.
from to

[ 2 ]

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Covered syllabus points

6. Chemical reactions question 1

Question (a)

Question (i)

Question (ii)

6. Chemical reactions question 2

Question (a)

Question (i)

Question (ii)

6. Chemical reactions question 3

Question (a)

Question (b)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question (v)

Question (vi)

6. Chemical reactions question 4

Question (a)

Question (i)

Question (ii)