Question

Equal masses of O₂, H₂ and CH₄ are kept under identical conditions of temperature and pressure. The ratio of the volumes occupied by them is:

• A. 2:16:2
• B. 2:16:1
• C. 1:16:2
• D. 1:1:1

Hint:

For equal mass, moles and hence volume are inversely proportional to molar mass.

Answer 1

The Correct Option is C

Pick a convenient equal mass and compute moles directly instead of working with ratios symbolically.

• Let the equal mass of each gas be 32 g, chosen because it divides evenly by all three molar masses.
• Moles of $O_2$ = $32/32 = 1$ mol.
• Moles of $H_2$ = $32/2 = 16$ mol.
• Moles of $CH_4$ = $32/16 = 2$ mol.
• At the same temperature and pressure, volume is proportional to moles, from $PV = nRT$, so the volumes are in the ratio $1 : 16 : 2$ for $O_2 : H_2 : CH_4$.
• This matches option C.