CAIE IGCSE Chemistry 6.3 Reversible Reactions and Equilibrium Topic Practice

CourseCourseConceptConceptDocumentDocument

Covered syllabus points

6.3.1—Some chemical reactions are reversible6.3.2—Changing the conditions can change the6.3.3—Reversible reaction in a closed system6.3.4—Predict and explain, for a reversible6.3.5—Symbol equation for the production of6.3.6—Sources of the hydrogen (methane) and6.3.7—Typical conditions in the Haber6.3.8—Symbol equation for the conversion of6.3.9—Sources of the sulfur dioxide (burning6.3.10—Typical conditions for the conversion6.3.11—Typical Haber and Contact process

Question 1

[Maximum number: 1]

When the colourless gas N2O4\mathrm{N}_{2} \mathrm{O}_{4} is heated, it forms the brown gas NO2\mathrm{NO}_{2}.
When the reaction mixture is cooled, the brown colour fades and turns back to colourless.
Which type of reaction is described by these observations?

A

decomposition

B

displacement

C

reduction

D

reversible

Question 2

[Maximum number: 2]

Complete the equation for the thermal decomposition of hydrated cobalt(II) nitrate.

2Co(NO3)2∙4H2O→….CoO+….NO2+O2+….H2O2 \mathrm{Co}\left(\mathrm{NO}_{3}\right)_{2} \bullet 4 \mathrm{H}_{2} \mathrm{O} \rightarrow \ldots . \mathrm{CoO}+\ldots . \mathrm{NO}_{2}+\mathrm{O}_{2}+\ldots . \mathrm{H}_{2} \mathrm{O}

Question 3

[Maximum number: 6]

Hydrogen iodide thermally decomposes into iodine and hydrogen. The reaction is reversible.

2HI( g) colourless gas →⇌I2( g) purple gas +H2( g) colourless gas \underset{\text { colourless gas }}{2 \mathrm{HI}(\mathrm{~g})} \rightarrow \underset{\substack{\mathrm{I}_{2}(\mathrm{~g}) \\ \text { purple gas }}}{\rightleftharpoons}+\underset{\substack{\mathrm{H}_{2}(\mathrm{~g}) \\ \text { colourless gas }}}{ }

Fig. 4.1 shows a gas syringe containing a mixture of hydrogen iodide, iodine and hydrogen gases. The gas syringe is sealed and the mixture is heated to 300∘C300^{\circ} \mathrm{C}. The mixture of gases reaches equilibrium and is purple.

Fig. 4.1

Fig. 4.1

Question (a)

(a)

State what is meant by the term equilibrium.

[ 2 ]

Question (b)

(b)

The pressure of the mixture is increased. All other conditions stay the same. The position of equilibrium does not change.

The colour of the gaseous mixture turns darker purple.
The temperature remains constant.

2HI( g) colourless gas =⇌I2( g) purple gas + colourless gas H2( g) colourless gas \underset{\text { colourless gas }}{2 \mathrm{HI}(\mathrm{~g})}=\underset{\substack{\mathrm{I}_{2}(\mathrm{~g}) \\ \text { purple gas }}}{\rightleftharpoons}+\underset{\substack{\mathrm{H}_{2}(\mathrm{~g}) \\ \text { colourless gas }}}{\text { colourless gas }}
[ 2 ]

Question (i)

(i)

Explain why the position of equilibrium does not change.

[ 1 ]

Question (ii)

(ii)

Suggest why the colour of the mixture of gases turns darker purple.

[ 1 ]

Question (c)

(c)

The temperature of the mixture of gases is decreased. All other conditions stay the same.

The mixture of gases turns lighter purple.
State what can be deduced about the forward reaction from this information.

[ 1 ]

Question (d)

(d)

Methanol is manufactured by reacting carbon monoxide with hydrogen.

CO( g)+2H2( g)⇌CH3OH( g)\mathrm{CO}(\mathrm{~g})+2 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{CH}_{3} \mathrm{OH}(\mathrm{~g})

The rate of formation of methanol increases when a catalyst is used.

[ 1 ]

Question (i)

(i)

State the effect on the position of equilibrium when a catalyst is used.

[ 1 ]

Question 4

[Maximum number: 2]

Hydrogen iodide thermally decomposes into iodine and hydrogen. The reaction is reversible.

2HI( g) colourless gas →⇌I2( g) purple gas +H2( g) colourless gas \underset{\text { colourless gas }}{2 \mathrm{HI}(\mathrm{~g})} \rightarrow \underset{\substack{\mathrm{I}_{2}(\mathrm{~g}) \\ \text { purple gas }}}{\rightleftharpoons}+\underset{\substack{\mathrm{H}_{2}(\mathrm{~g}) \\ \text { colourless gas }}}{ }

Fig. 4.1 shows a gas syringe containing a mixture of hydrogen iodide, iodine and hydrogen gases. The gas syringe is sealed and the mixture is heated to 300∘C300^{\circ} \mathrm{C}. The mixture of gases reaches equilibrium and is purple.

Fig. 4.1

Fig. 4.1

State what is meant by the term equilibrium.

Question 5

[Maximum number: 1]

Some information about three gases, P, Q and R, is listed.
- Gas P forms when magnesium reacts with dilute hydrochloric acid.
- Gas Q makes up 78% of the air.
- Gas R forms when gas P reacts with gas Q.

What is gas R ?

A

ammonia

B

methane

C

nitrogen dioxide

D

water vapour

Question 6

[Maximum number: 1]

Which statements about the Haber process are correct?
1 One of the raw materials is extracted from liquid air by fractional distillation.
2 One of the raw materials is produced by the reaction of steam and methane.
3 The catalyst for the Haber process is vanadium(V) oxide.

A

1 only

B

1 and 2 only

C

2 and 3 only

D

1, 2 and 3

Question 7

[Maximum number: 1]

Ammonia is produced using the Haber process.
Which row shows the source of the raw materials and the reaction conditions?

source of
nitrogen

source of
hydrogen

temperature
1∘C1{ }^{\circ} \mathrm{C}

pressure
/atm

air

hydrocarbons

200

200

hydrocarbons

air

450

2

air

hydrocarbons

450

200

air

hydrocarbons

450

2

Question 8

[Maximum number: 1]

The flow chart shows part of the process for the manufacture of sulfuric acid and its electrolysis.

Figure for Question 8 — CAIE IGCSE Chemistry

What are gases 1,2 and 3 ?

gas 1

gas 2

gas 3

sulfur dioxide

hydrogen

sulfur trioxide

sulfur dioxide

oxygen

sulfur trioxide

sulfur trioxide

hydrogen

sulfur dioxide

sulfur trioxide

oxygen

sulfur dioxide

Question 9

[Maximum number: 1]

Which raw material is used in the Contact process?

A

air

B

ammonia

C

carbon

D

nitrogen

Question 10

[Maximum number: 1]

Which row identifies the pressure and the catalyst used for the conversion of sulfur dioxide to sulfur trioxide in the Contact process?

pressure/atm

catalyst

2

iron

2

vanadium(V) oxide

200

iron

200

vanadium(V) oxide

Question 11

[Maximum number: 1]

Which row explains why a high temperature and an iron catalyst are used in the manufacture of ammonia by the Haber process?

high temperature

iron catalyst

increases the rate of the reaction

increases the equilibrium yield of ammonia

increases the rate of the reaction

increases the rate of the reaction

increases the equilibrium yield of ammonia

increases the equilibrium yield of ammonia

increases the equilibrium yield of ammonia

increases the rate of the reaction

All question bank results loaded