Which of the following gases is/are lighter than air?
1. Hydrogen chloride
2. Sulfur dioxide
3. Helium
Select the correct answer from the code given below:
- AOnly 1
- B2 and 3
- COnly 3
- D1 and 2
Show answer and explanation
Correct answer: (c) Only 3
Explanation
A gas is lighter than air only if its molar mass is below that of air (≈29 g/mol).
Helium (4 g/mol) is lighter; HCl (36.5 g/mol) and SO₂ (64 g/mol) are both heavier than air.