Agas diffuses 1/8 times faster than hydrogen gas. what is the molar mass of the gas?
129.02 g/mol
136.44 g/mol
140.81 g/mol
145.45 g/mol

129.02 g/mol.

Explanation:

∨ ∝ 1/√M.

where, ∨ is the rate of diffusion of the gas.

M is the molar mass of the gas.

∵ ∨₁/∨₂ = √(M₂/M₁).

∨₁ is the rate of effusion of H₂ gas.

∨₂ is the rate of effusion of the unknown gas.

M₁ is the molar mass of H₂ gas (M₁ = 2.016 g/mol).

M₂ is the molar mass of the unknown gas (M₂ = ??? g/mol).

∨₂ = 1/8∨₁

∨₁/∨₂ = 8.0.

∵ ∨₁/∨₂ = √(M₂/M₁)

∴ (8.0) =√(M₂)/(2.016 g/mol)

∴ (8.0)² = (M₂)/(2.016 g/mol)

∴ M₂ = (8.0)²(2.016 g/mol) = 129.024 g/mol ≅ 129.02 g/mol.