Gas Laws

Ideal gas law works best at high temperature and low pressure. It becomes inaccurate at high pressures (gas molecules have volume) and low temperatures (intermolecular forces become significant). Real gases deviate more when near their condensation point.

Dalton's Law: Ptotal = P1 + P2 + P3 + ... Each gas exerts pressure independently. Partial pressure Pi = (ni/ntotal) x Ptotal = Xi x Ptotal, where Xi is the mole fraction. For gases collected over water, subtract water vapor pressure from total pressure.

Rate1/Rate2 = sqrt(M2/M1) where M is molar mass. Lighter gases effuse and diffuse faster. Effusion is escape through a tiny hole; diffusion is mixing of gases. The ratio of rates equals the inverse square root ratio of molar masses.