Everyday Science · Environment, Weather & Ecology · page 3 of 3

Composition of Atmosphere MCQs with Answers

Includes 3 past paper MCQs (marked).

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Composition of Atmosphere MCQs (21–25)

5 MCQs with answers and a short one-liner. Hide answers to test yourself.

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21.
Second most abundant constituent of dry air in terms of volume after nitrogen is?
Correct Answer: A. Oxygen
One-liner
The second most abundant constituent of dry air by volume after nitrogen is oxygen, which makes up about 21% of the atmosphere.
22.
What percentage of CO2 is present in the atmosphere?
Correct Answer: A. 0.032%
One-liner
Carbon dioxide (CO₂) constitutes approximately 0.032% of the Earth's atmosphere by volume.
23.
The percentage of Oxygen in the air is _?
Correct Answer: D. 20.94%
One-liner
Oxygen makes up approximately 20.94% of the Earth's atmosphere by volume.
24.
Which of the following noble gases is not present in the atmosphere?
Correct Answer: C. Radon (Rn)
One-liner
Radon (Rn) is the noble gas that is not present in the atmosphere in appreciable amounts; it is produced by the radioactive decay of uranium and thorium in rocks and soil.
25.
Air contains ?
Correct Answer: D. 78% Nitrogen
One-liner
Air contains 78% Nitrogen, making it the most abundant gas in Earth's atmosphere.