The density of a certain gas is 1.98gdm−³ at s.t.p. What is the molecular mass of the gas?

A. 44.0 g
B. 54.0 g
C. 26.0 g
D. 31.0 g

Correct Answer:

Option A – 44.0 g

Explanation

Density = mass/volume
∴ 1.98 = molecular mass/22.4
molecular mass = 1.98 X 22.4 = 44.35 ≅ 44.05