Gases in the Atmosphere | Edexcel IGCSE Chemistry Exam Questions 2019

1a4 marks

This question is about gases in the atmosphere.

The box gives the names of some gases in the atmosphere.

argon

carbon dioxide

helium

nitrogen

oxygen

Choose gases from the box to answer these questions.

Each gas may be used once, more than once or not at all.

i)

Identify a noble gas.

(1)

ii)

Identify a gas that makes up about 78% of the atmosphere.

(1)

iii)

Identify a greenhouse gas.

(1)

iv)

Identify a gas produced by the thermal decomposition of calcium carbonate.

(1)

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1b2 marks

Sulfur reacts with oxygen to produce sulfur dioxide gas.

i)

Write a chemical equation for this reaction.

(1)

ii)

State an environmental problem caused when sulfur dioxide gas dissolves in water in the atmosphere.

(1)

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2a1 mark

A student uses this apparatus to investigate the effect of heat on different solid metal carbonates.

1cr-q5

This is the student’s method:

Use a spatula to put some metal carbonate in the boiling tube
Fit the delivery tube into position
Pour some limewater into the test tube
Start a timer and immediately begin to heat the metal carbonate
Record the time when a change first occurs in the limewater

The student repeats the method using different metal carbonates.

When a metal carbonate is heated a reaction sometimes occurs.
The equation for the reaction is:

metal carbonate → metal oxide + carbon dioxide

State the name given to this type of reaction.

How did you do?

2b2 marks

State two variables that the student should control in this investigation.

1. ...........................................

2. ...........................................

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2c1 mark

Suggest why bubbles appear in the limewater immediately after heating has started but before there is any change to the metal carbonate.

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2d2 marks

Explain the purpose of limewater in this investigation.

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2e3 marks

The table shows some of the results for the student’s investigation.

Metal carbonate	Colour change of solid	Time taken for any change in limewater
calcium carbonate	remains white	90 seconds
sodium carbonate	remains white	no change
copper(II) carbonate		50 seconds

i)

State the colour change that occurs for copper(II) carbonate.

from ...................................... to ...................................

(2)

ii)

Give a chemical equation for this reaction of copper(II) carbonate.

(1)

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2f3 marks

f)

There is a relationship between the position of a metal in the reactivity series and how easily the metal carbonate reacts when heated.

I)

Use the student’s results and your own knowledge to deduce this relationship.

(2)

ii)

State how you should extend the investigation to see if your deduction is correct.

(1)

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3a4 marks

This question is about determining the percentage composition by volume of a mixture of three gases, oxygen, carbon dioxide and argon in air.

Two experiments are done to determine the percentage composition by volume of oxygen.

In experiment 1, a student connects a gas syringe to a conical flask filled with iron filings. The diagram shows the apparatus the student uses.

i)

Give two changes the student needs to make to the apparatus in experiment 1 to find the percentage by volume of oxygen in a sample of air.

(2)

In experiment 2, two 100 cm³ gas syringes are connected to a reaction tube containing copper powder. The sample of air is passed over hot copper oxide. The diagram shows the apparatus that is used.

ii)

Explain why both syringes should not be filled with 100 cm³ of oxygen.

(2)

How did you do?

3b

3 marks

When the apparatus in experiment 2 is set up correctly, the mixture of gases is passed over the hot copper powder.

The total volume of the mixture of gases in the syringes at the start is 76 cm³.

The total volume of the mixture of gases in the syringes at the end is 64 cm³.

i)

Calculate the percentage by volume of oxygen in the mixture of gases.

(2)

ii)

Explain how the answer to part (i) suggests that all of the oxygen has not reacted.

(1)

How did you do?

3c4 marks

To determine the percentage of carbon dioxide in the air, the student suggests adapting the apparatus in experiment 2.

They suggest replacing the reaction tube containing copper powder with a conical flask containing limewater, as shown.

Explain why this experiment will not show the presence of carbon dioxide and give two reasons why this experiment will not allow the percentage of carbon dioxide in the air to be determined.

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3d2 marks

The percentage by volume of argon cannot be determined directly because it is very unreactive.

Explain why argon is extremely unreactive.

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☐	A	1
☐	B	20
☐	C	25
☐	D	78

☐	A	When bubbled through limewater, carbon dioxide turns limewater cloudy
☐	B	It is produced when copper(II) carbonate undergoes thermal decomposition
☐	C	It is the third most abundant gas in the atmosphere
☐	D	It is a greenhouse gas that contributes to climate change

☐	A	hydrogen
☐	B	methane
☐	C	neon
☐	D	nitrogen

☐	A	0.04%
☐	B	0.9%
☐	C	21%
☐	D	35%

cracking an alkane
complete combustion of an alkane
reaction between magnesium and hydrochloric acid
rusting of iron
thermal decomposition of copper(II) carbonate

syringe reading at start / cm³	76
syringe reading at end / cm³
volume of oxygen used / cm³

volume of air in conical flask / cm³	100
volume of air in connecting tube / cm³	10
original volume of air in syringe / cm³	80
final volume of air in syringe / cm³	43

Possible cause	Effect on volume of oxygen used
wet iron filings not in excess
apparatus left for 1 hour instead of 1 week
apparatus left in a warmer place for 1 week

Step K:	Place some damp iron wool and a rubber bung in the top of the tube
Step L:	Leave the apparatus for a few days
Step M:	Place a graduated glass tube in a beaker of water
Step N:	Record the reading of the water level in the tube
Step O:	Record the reading of the water level again

☐	A	M, K, N, L, O
☐	B	K, M, N, L, O
☐	C	M, N, K, L, O
☐	D	K, M, N, L, O

Time in minutes	Volume of gas in tube in cm³
0	48.5
1	41.0
2	38.0
4	37.5
5	37.0
6	37.0
7	37.0

☐	A	LiCO₃ → LiO + CO₂
☐	B	Mg₂CO₃ → Mg₂O + CO₂
☐	C	CaCO₃ + CO₂→ CaO
☐	D	CuCO₃ → CuO + CO₂

☐	A	Combustion reactions are also reduction reactions
☐	B	During the combustion of sulfur, a blue flame is observed and a colourless, poisonous gas is produced
☐	C	All combustion reactions are endothermic
☐	D	The balanced symbol equation for the combustion of hydrogen is: H₂ + O₂ → H₂O₂

Reading number	Reading on syringe A in cm³
Start	78
1	70
2	67
3	65
4	63
5	61
6	60
7	59
8	58
9	58
10	58

Gases in the Atmosphere (Edexcel IGCSE Chemistry)

Exam Questions