Question

On a given day, the weatherman reports that the atmospheric pressure is 50F, and the relative humidity is 45%. If the (pure) vapor pressure of water at 50F is 9.2 torr, then the partial pressure of water in the atmosphere is?

Answer 1

data given by the problem statement:

the atmosphric pressure =50F

the relative humidity = 45%

the pure vapoure pressure of water = 9.2torr

the partial pressure of water in the atmosphere=?

the answer is "the vapoure pressure of water in the atmosphere is equal to partial pressure"

because according to Dalton's law and Roult's law as follows respectively

• the mixture of non reacting gases, the total pressure is equal to the parrtial pressure of the individual gases
• "the partial vapour pressure of each component of an ideal mixture of liquids is equal to the vapour pressure of the pure component multipied its mole fraction in the mixture

hence partial pressure of water in atmosphere does not influenced by change in the humidity.