Dalton’s Law of Partial Pressures

Dalton’s law of partial pressure At constant volume and temperature, the total pressure of a mixture of gases is the sum of the partial pressures of all the gases present. Ptotal = P1 + P2 + P3…

Example 1 What is the partial pressure of O2 (PO2) at 1 atm if PN2 = 593.4 mm Hg, PCO2 = 0.3 mm Hg, and Pothers = 7.1 mm Hg? Ans: 159.2 mmHg

Example 2 Determine the total pressure of a gas mixture that contains O2, N2, and He if PO2 = 150 mmHg, PN2 = 350 mm Hg, PHe = 200 mm Hg. Ans: 700 mmHg

Mole Fraction and Partial Pressures Mole Fraction – a dimensionless quantity that expresses the ratio of moles of one component to moles of all components present. Xi = Moles i Total Moles *** (i = individual gas)

PH2O = (0.0287) (.977 atm) = .0280 atm