Partial Pressure Calculator
Calculate partial pressure of gases in a mixture using Dalton's Law, find mole fractions, or use Raoult's Law for solution vapor pressures.
What is Dalton's Law of Partial Pressures?
Dalton's Law states that the total pressure of a gas mixture equals the sum of the partial pressures of each component gas: P_total = P₁ + P₂ + P₃ + ... Each gas in a mixture exerts pressure independently as if it alone occupied the container.
How do I calculate partial pressure from mole fraction?
For gas i in a mixture: P_i = X_i × P_total, where X_i is the mole fraction. For example, if a gas mixture is 80% N₂ (X=0.80) at 5 atm total pressure, P_N₂ = 0.80 × 5 = 4 atm. This is the fundamental relationship connecting mole fraction to partial pressure.
What is mole fraction in gas mixtures?
Mole fraction (X) of a gas is the ratio of moles of that gas to total moles in the mixture. For gas A in a mixture: X_A = n_A / (n_A + n_B + n_C + ...). All mole fractions sum to 1. In gases, mole fraction equals volume fraction at same conditions.
How do I use Raoult's Law for partial pressure?
Raoult's Law: P_i = X_i × P°_i, where P°_i is the pure component vapor pressure. Used for vapor-liquid equilibrium in solutions. For ideal solutions, partial pressure equals mole fraction times pure vapor pressure. Deviations occur in non-ideal solutions.
What is the difference between partial pressure and vapor pressure?
Vapor pressure is the pressure exerted by a pure substance's vapor in equilibrium with its liquid at a given temperature. Partial pressure is the pressure a component contributes to a gas mixture's total pressure. In a mixture above a liquid, partial pressure of the volatile component equals its vapor pressure.
How is partial pressure used in diving and medicine?
In SCUBA diving, the partial pressure of oxygen determines toxicity risk. At 1 atm air (21% O₂), pO₂ = 0.21 atm. At 30m depth (4 atm), pO₂ = 0.84 atm. In medicine, oxygen therapy uses partial pressures - blood oxygen partial pressure (pO₂) indicates how well lungs transfer oxygen to blood.