A mixture of helium and neon gases has a density of 0.6048 g/L at 48.7°C and 792 torr. What is the mole fraction of neon in this mixture?

The volume of one mole of gas is 22.4 liters at 0 °C and 760 Torr. The volume of the given condition can be calculated using:

(PV) / T = constant

(P₁V₁) / T₁ = (P₂V₂) / T₂

(760 * 22.4) / 273 = (792 * V₂) / 321.7

V₂ = 25.3 Liters

The Mr of He = 4

The Mr of Ne = 20

Density of He = 4/25.3 = 0.1581 g/L

Density of Ne = 20/25.3 = 0.7905 g/L

Let x be the fraction of Ne

1 - x is the fraction of He

avg density = sum[ (mole fraction * Mr) / V]

0.6048 = (20x + 4 (1 - x)) / 25.3

x = 0.70