In an experiment, 201 mL of wet hydrogen gas is collected over water at 27 degrees Celsius and a barometric pressure of 733 torr. What is the partial pressure of hydrogen in this experiment in atm?

Question

vapor pressure of water at 27 degrees Celsius is 26.74 torr.

Zinc reacts with aqueous sulfuric acid to form hydrogen gas.

Answer 1

When a gas is collected over water, to find the pressure of the gas alone, one must subtract the vapor pressure of water at the temperature at which the gas is collected.

Pressure of hydrogen gas = 733 torr - 26.74 torr = 706.26 torr

Total pressure in atmospheres = 733 torr x 1 atm/760 torr = 0.9645 atm

Pressure of hydrogen in atmospheres = 706.26 torr x 1 atm/760 torr = 0.9293 atm

Partial pressure of hydrogen = 0.9293 atm/0.9645 atm = 0.963 atm (3 significant figures)