Question

A gaseous mixture contains 421.0 Torr of H2(g), 392.9 Torr of N2(g), and 68.1 Torr of Ar(g). Calculate the mole fraction, X, of each of these gases.

Answer 1

Total pressure of the gaseous mixture is , P = 421.0 + 392.9 +68.1 = 882 torr

Let p₁ = partial pressure H₂ gas

X₁ = mole fraction of H₂ gas

We know that partial pressure = mole fraction x partial pressure

p₁ = X₁ x P

X₁ = P1/P

But P = (nRT) /V         ----(1)

So p₁ = (n₁RT)/V        ---(2)

Eqn(2) / Eqn(1) gives

p₁ / P = n₁ / n = mole fraction of H₂ gas

Therefore ratio of partial pressure gas/total pressure = mole fraction individual gas

Mole fraction of H₂ = partial pressure of H₂ / total pressure

                            = 421.0 / 882

                            = 0.48

Mole fraction of N₂ = partial pressure of N₂ / total pressure

                            = 392.9 / 882

                            = 0.44

Mole fraction of Ar = partial pressure of Ar / total pressure

                            = 68.1 / 882

                            = 0.077