AQA GCSE Chemistry

Topic Questions

9.1 Formation of Earth's Atmosphere

11 mark

The Earth's atmosphere has evolved over the past 4.6 billion years. 

Which option correctly shows what has happened to the proportion of each gas during this time period?

  Oxygen Nitrogen Carbon dioxide Water vapour
A increased decreased decreased decreased
B increased increased decreased decreased
C decreased increased increased increased
D increased decreased increased increased

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21 mark

What is the approximate percentage of oxygen in the current atmosphere? 

  • 4%

  • 21%

  • 55%

  • 78%

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31 mark

The proportion of carbon dioxide has decreased since the early atmosphere.

One reason for this is plants undergoing photosynthesis. 

What other reasons are there for the decrease in carbon dioxide levels?

  Reason 1  Reason 2 
A farming animals burning fossil fuels
B deforestation carbonates forming sediments 
C locked up in sedimentary rock dissolved in the ocean
D given out by plants during photosynthesis  trapped in fossil fuels 

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41 mark

It is thought that algae used gases in the atmosphere to form amino acids. 

The diagram shows the amino acid, alanine.

9-1

Which gases in the early atmosphere were the most likely sources of these elements?

  • Water vapour, carbon dioxide, ammonia

  • Ammonia, methane, oxygen 

  • Carbon dioxide, methane, water vapour 

  • Nitrogen, carbon dioxide, oxygen

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51 mark

Green plants undergo photosynthesis. 

Which numbers correctly balance the symbol equation for photosynthesis? 

 __ CO+  __ H2O       →    __ C6H12O  +   __ O2

  • 6, 6, 1, 2

  • 6, 12, 2, 6

  • 6, 3, 1, 3

  • 6, 6, 1, 6

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