1. Dalton’s Law of Partial Pressures

2. 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…

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

4. 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

5. 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)

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