400 mL of hydrogen are collected over water at 18 C and a total pressure of 740 mm of mercury. (Vapor pressure of H2O at 18 C=15.5mm).

a) What is the partial pressure of H2O?

b) What is the partial pressure of H2?

a)15.5 mmHg is the partial pressure of water vapor.

b) 724.5 mmHg is the partial pressure of hydrogen gas.

Explanation:

Total pressure of gases = T = P = 740 mmHg

Vapor pressure of the water =

Partial pressure of the hydrogen gas =

Partial pressure of the water =

15.5 mmHg is the partial pressure of water vapor.

Using Dalton's law of partial pressure:

724.5 mmHg is the partial pressure of hydrogen gas.