GCSE Edexcel Chemistry Identifying gases: A student used the internet to f

Question

A student used the internet to find information about the percentages of different gases in the Earth’s early atmosphere.
She was surprised to find the information given on two websites was very different.

The information from the two websites is shown in the table.

| gas              | percentage gas in atmosphere (%) |    | gas              | percentage gas in atmosphere (%) |
|------------------|----------------------------------|----|------------------|----------------------------------|
| hydrogen         | 60                               |    | carbon dioxide    | 92.2                             |
| water vapour     | 20                               |    | nitrogen          | 5.1                              |
| carbon dioxide    | 20                               |    | sulfur dioxide    | 0.4                              |
| hydrogen sulfide  | 6                                |    | hydrogen sulfide  | 0.4                              |
| nitrogen         | 6                                |    | ammonia          | 0.1                              |
| methane          | 1                                |    | methane          | 0.1                              |

a) One of the gases in the table is present in a much larger amount in today’s atmosphere.
State the name of this gas.

b) A gas not named in the table makes up about 21% of today’s atmosphere.
State the name of this gas.

c) Complete the sentence by putting a cross (X) in the box next to your answer.
The amount of carbon dioxide in the early atmosphere was reduced by

A) animals breathing
B) volcanic activity
C) deforestation
D) the gas dissolving in oceans

d) The information given on two websites is very different.
Explain why it is difficult to be certain about the composition of the Earth’s early atmosphere.

e) In an experiment to find the percentage of oxygen in the air, some copper was heated in 50.0 cm³ of dry air.

All of the oxygen in this sample of air reacted to form copper oxide.

After the reaction, the volume of gas remaining was 41 cm³.

i) Calculate the percentage of oxygen in this sample of air.

ii) The word equation for the reaction is

copper + oxygen → copper oxide

Balance the equation for this reaction by putting numbers in the spaces provided.

Cu + O₂ → CuO

A student used the internet to find information about the percentages of different gases in the Earth’s early atmosphere - Edexcel - GCSE Chemistry - Question 1 - 2013 - Paper 1

Worked Solution & Example Answer:A student used the internet to find information about the percentages of different gases in the Earth’s early atmosphere - Edexcel - GCSE Chemistry - Question 1 - 2013 - Paper 1

a) One of the gases in the table is present in a much larger amount in today’s atmosphere. State the name of this gas.

b) A gas not named in the table makes up about 21% of today’s atmosphere. State the name of this gas.

c) Complete the sentence by putting a cross (X) in the box next to your answer. The amount of carbon dioxide in the early atmosphere was reduced by

d) The information given on two websites is very different. Explain why it is difficult to be certain about the composition of the Earth’s early atmosphere.

e) i) Calculate the percentage of oxygen in this sample of air.

e) ii) The word equation for the reaction is. Balance the equation for this reaction by putting numbers in the spaces provided.

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