Air Composition — Homi Bhabha Class 9 Chemistry MCQs with Solutions
Free Homi Bhabha Class 9 Chemistry Air Composition MCQs with step-by-step solutions (8 questions). Part of Substances in Daily Use & Applied Chemistry. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Air Composition · medium · theory
The most abundant gas in the Earth's atmosphere is:
A. nitrogen ✓ Correct
B. argon
C. oxygen
D. carbon dioxide
Solution: Nitrogen makes up about 78% of the air by volume.
Q2 — Air Composition · medium · theory
The percentage of oxygen in the air is approximately:
A. 50%
B. 78%
C. 1%
D. 21% ✓ Correct
Solution: Oxygen makes up about 21% of the atmosphere.
Q3 — Air Composition · hard · theory
The approximate percentage of carbon dioxide in normal air is:
A. about 21%
B. about 10%
C. about 78%
D. about 0.04% ✓ Correct
Solution: CO₂ is a minor component, only about 0.03–0.04% of the air.
Q4 — Air Composition · hard · theory
The most abundant noble gas present in air is:
A. neon
B. krypton
C. helium
D. argon ✓ Correct
Solution: Argon makes up about 0.9% of the atmosphere — the most abundant noble gas in air.
Q5 — Air Composition · medium · theory
Which gas in the air is essential for the process of respiration and burning?
A. nitrogen
B. oxygen ✓ Correct
C. carbon dioxide
D. argon
Solution: Oxygen supports respiration and combustion.
Q6 — Air Composition · easy · theory
By volume, the most abundant gas in clean, dry air is
A. argon
B. carbon dioxide
C. oxygen
D. nitrogen ✓ Correct
Solution: Clean dry air is about 78 percent nitrogen and about 21 percent oxygen by volume. Nitrogen is therefore the most abundant gas in air, while carbon dioxide and argon are present in much smaller amounts.
Q7 — Air Composition · medium · theory
Although it makes up only about one-fifth of the air, one gas is vital because it supports both burning and the breathing of living things. That gas is
A. water vapour
B. nitrogen
C. oxygen ✓ Correct
D. carbon dioxide
Solution: Oxygen, about 21 percent of air by volume, is needed for combustion (burning) and for respiration in living organisms. Nitrogen does not support burning, and carbon dioxide is present in only tiny amounts.
Q8 — Air Composition · hard · numerical
Air contains roughly 21 percent oxygen by volume. What volume of oxygen is present in 500 litres of air?
A. 42 litres
B. 210 litres
C. 21 litres
D. 105 litres ✓ Correct
Solution: Volume of oxygen = 21 percent of 500 = (21 / 100) × 500 = 105 litres. So about 105 litres of the 500 litres of air is oxygen.