Ideal Gas Law Calculator

R = 8.314 J/(mol*K) = 0.08206 L*atm/(mol*K) = 1.987 cal/(mol*K) = 62.36 L*mmHg/(mol*K). Choose units matching your other quantities. R = N_A * k_B where k_B = 1.381e-23 J/K is Boltzmann's constant.

Standard Temperature and Pressure: 0 degrees C (273.15 K) and 1 atm. One mole of ideal gas at STP occupies 22.414 L. Note: IUPAC changed STP to 0 degrees C and 1 bar (0.987 atm) in 1982, giving 22.711 L/mol.

At high pressures (>10 atm), low temperatures, and near condensation/liquefaction points. Real gases deviate due to finite molecular size (b correction) and intermolecular attractions (a correction) described by the van der Waals equation.

M = rho*RT/P, where rho is density in g/L. Measuring gas density at known T and P gives the molar mass. This is Dumas's method for determining molar masses of volatile liquids.

For a mixture of ideal gases, total pressure P_total = P_1 + P_2 + ... where each partial pressure P_i = n_i*R*T/V. Each gas behaves independently and exerts the pressure it would have if it alone occupied the full volume.

At constant T and P, equal volumes of all ideal gases contain equal numbers of molecules (or moles). This follows directly from the ideal gas law: V/n = RT/P = constant at constant T and P.

The kinetic molecular theory models gas molecules as point particles in random motion with elastic collisions. It derives PV = nRT from first principles: P = (1/3)*(n/V)*m*v_rms^2, giving the microscopic interpretation of temperature as proportional to mean kinetic energy.

v_rms = sqrt(3RT/M) where M is molar mass in kg/mol. For N2 at 298 K: v_rms ~ 515 m/s. Lighter molecules (H2, He) have much higher speeds, explaining why hydrogen and helium escape from Earth's atmosphere over geologic time.

Yes, using Dalton's law: P_total = (n_total * R * T) / V, where n_total is the sum of all moles of gas. Individual partial pressures are P_i = x_i * P_total, where x_i = n_i/n_total is the mole fraction.