Question

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?

Answer 1

Answer:

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 = $p_1=15.5 mmHg$

Partial pressure of the hydrogen gas = $p_2=?$

Partial pressure of the water = $p_1=15.5 mmHg$

15.5 mmHg is the partial pressure of water vapor.

Using Dalton's law of partial pressure:

$P=p_1+p_2$

$740 mmHg=15.5 mmHg+p_2$

$p_2=740 mmHg-15.5mmHg =724.5 mmHg$

724.5 mmHg is the partial pressure of hydrogen gas.