Question

H2 is collected over water at 22C and 745 torr. what is the partial pressure of the hydrogen if the vapor pressure of water at 22C is equal to 20.0 torr?

Answer 1

whenever a gas is collected over water, a small amount of water vapor always comes along for the ride. The total pressure in the container, P_total, is always made up of 2 pieces: the gas that was collected, PLUS the small amount of water vapor.\[P_{total} = P_{gas} + P_{H2O}\] In this case, the total pressure is given, as well as the partial pressure of the water vapor. Find the pressure of the gas