Gas Mixture Molar Mass Calculator

Gas Mixture Molar Mass Calculator

A gas mixture does not have a single "molar mass" the way a pure substance does - it has an average, weighted by how much of each component is actually present.

The Formula

M_mix = x₁ × M₁ + x₂ × M₂

Worked Example

A mixture that is 79% nitrogen (28.01 g/mol) and 21% oxygen (32.00 g/mol) by mole fraction - essentially air: M_mix = 0.79 × 28.01 + 0.21 × 32.00 ≈ 28.85 g/mol, closely matching real air's accepted average molar mass of about 28.97 g/mol.

How to Use This Calculator

1. Enter the mole fraction of gas 1 (0 to 1).
2. Enter the molar mass of gas 1 and gas 2.

Related: Gas Specific Gravity Calculator, which uses this mixture molar mass directly.