Answer:
a)15.5 mmHg is the partial pressure of water vapor.
b) 724.5 mmHg is the partial pressure of hydrogen gas.
Step-by-step 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.