AQA GCSE Chemistry (8462), Higher tier · Chemistry of the atmosphere › Composition and evolution of the atmosphere
Practise Proportions of gases in the atmosphere. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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What is the approximate percentage of oxygen in the Earth's atmosphere?
20%
The final volume of gas was 79 cm3. Calculate the percentage of oxygen in the air.
21%
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
(a) Which gas makes up about four-fifths of the Earth's atmosphere? Tick (✓) one box.[1]
Argon
Carbon dioxide
Nitrogen
Oxygen
(b) What is the approximate percentage of oxygen in the Earth's atmosphere?[1]
(c) Name two other gases found in small proportions in the atmosphere.[2]
(d) For about how long have the proportions of gases in the atmosphere been much the same as they are today?[1]
Show the answer and mark scheme
(a)Answer: Nitrogen
(b)Answer: 20%
20 (%)
(c)
carbon dioxide
water vapour
argon / (other) noble gases
(d)
(about) 200 million years
Question 2Medium5 marks
A classroom contains 150 m3 of air.
(a) Calculate the approximate volume of nitrogen in the classroom.[2]
(b) Air contains about 0.04% carbon dioxide. Calculate the volume of carbon dioxide in the classroom.[2]
(c) The percentage of carbon dioxide in the classroom air increased during a lesson. Suggest why.[1]
Show the answer and mark scheme
(a)Answer: 120 m3
80 ÷ 100 × 150
120 (m3)
(b)Answer: 0.06 m3
0.04 ÷ 100 × 150
0.06 (m3)
(c)
the people in the room breathe out carbon dioxide (produced by respiration)
Question 3Hard6 marks
A student used this method to find the percentage of oxygen in air.
Two gas syringes were connected by a tube containing copper powder.
One syringe contained 100 cm3 of air at the start.
The copper was heated strongly and the air was pushed backwards and forwards over the hot copper until the volume stopped changing.
The apparatus was allowed to cool and the final volume of gas was measured.
(a) Explain why the volume of gas decreased.[2]
(b) The final volume of gas was 79 cm3. Calculate the percentage of oxygen in the air.[1]
(c) Explain why the apparatus was allowed to cool before the final volume was measured.[1]
(d) The student repeated the experiment. This time the final volume was 83 cm3. Suggest one reason for the different result.[1]
(e) Name the main gas left in the syringe at the end.[1]
Show the answer and mark scheme
(a)
oxygen (in the air) reacted with the copper
to form (solid) copper oxide, so oxygen was removed from the gas
(b)Answer: 21%
21 (%)
(c)
gases expand when hot, so the volume measured would be too high
(d)
not all the oxygen reacted (e.g. not enough copper / not passed over the copper enough times / not heated for long enough) / air leaked into the apparatus