Question

A 10 g mixture of hydrogen and helium is contained in a vessel of capacity 0.0125 m3 at 6 bar and 27°C. The mass of helium in the mixture is _______ g. (nearest integer)
Given : R = 8.3 J K–1 mol–1
(Atomic masses of H and He are 1 u and 4 u, respectively)

Answer 1

Number of moles of mixture of H2 and He

$=\frac{PV}{RT}$

$=\frac{6×10^5×0.0125}{8.3×300}=3$

Let the mass of He in 10 g mixture be x g

∴$\frac{x}{4}+\frac{10−x}{2}=3$

On solving x = 8 g

∴ Mass of He in the mixture = 8 g