Gas density vs molecular weight

Relationship between molecular weight and gas density at STP, and implications for flow calculations.

At STP, gas density is proportional to molecular weight. The relationship: density (g/L) = MW (g/mol) ÷ 22.414 (L/mol).

Heavier gases (Ar, N2, O2) have higher densities than lighter gases (H2, He). This affects mass flow conversion: for the same volumetric flow (sccm), a heavier gas delivers more mass per minute.

For process design, use NIST reference data for accurate gas properties. Deviations from ideal gas behavior can occur at high pressure or low temperature.