The air in a 22 C room contains water at a partial pressure of 14 mm Hg. What is the relative humidity?

70.35%

Explanation:

The relative humidity is a percentage and is the ratio between the partial pressure of water and the vapor pressure of water times 100% The partial pressure gives you an idea of the amount of water in the air whereas the vapor pressure is related with the maximum amount of water that can be in the air for a given temperature.

Vp (h2o) - > Vapor pressure of water

p (h2o) - > Partial pressure of water

RH - > Relative humidity

Vp (h20) at 22°C = e^ (20.386 - (5132 / (temperature + 273)) = 19.9 Torr

(1 Torr = = 1 mm Hg)

RH = p (h2o) / Vp (h2o) * 100% = (14/19.9) * 100% = 70.35%

Note: The formula used to find the vapor pressure of water is an approximation, to get a better value you could use a table to determine the vapor pressure of water at a certain temperature. Remember that Vp (h2o) is a constant for a given temperature.