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Gases in the atmosphere

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Question 2

Dry, unpolluted air is a mixture of different gases, mainly nitrogen and oxygen.

a.

(i) State the approximate percentage by volume of nitrogen in dry, unpolluted air.

(ii) Argon makes up about 0.93%0.93\%0.93% of dry air. State the chemical symbol for argon and explain why it is extremely unreactive.

[3]
b.

Give the name or formula of a gas often present in polluted air that is a major cause of acid rain.

[1]
c.

A student carried out an experiment to determine the percentage of oxygen in a sample of air using the apparatus shown below.

An experimental setup involving a test tube inverted in a beaker of water. At the very top (the closed bottom) of the inverted test tube is a plug of wet iron wool. Below this wool, there is a column of air trapped inside the test tube. The lower, open end of the test tube is placed under water in a beaker, meaning some water rises up into the bottom of the tube.

The student recorded the following results after leaving the experiment to run for one week:

  • Initial height of air column: 125 mm125\text{ mm}125 mm
  • Final height of air column: 99 mm99\text{ mm}99 mm

(i) Some of the iron turned into rust. Write the word equation for this reaction.

(ii) Use the student's results to calculate the percentage of oxygen by volume in this sample of air. Give your answer to one decimal place.

[3]
d.

The student left the apparatus in place for an additional week. How could they use a further measurement to confirm that all of the oxygen had reacted during the first week?

[1]

Gases in the atmosphere Questions

  1. IGCSE
  2. /Chemistry
  3. /Gases in the atmosphere