Question

Zinc metal is added to hydrochloric acid to generate hydrogen gas and is collected over a liquid whose vapor pressure is the same as that of pure water at 20.0°C (18 torr). The volume of the mixture is 1.7 L, and its total pressure is 0.610 atm. Determine the partial pressure of the hydrogen gas in this mixture.
a. 446 torr
b. 788 torr
c. 758 torr
d. 464 torr
e. 482 torr

Answer 1

Answer :  The correct option is, (A) 446 torr

Solution :

According to the Dalton's law, the total pressure of the gas is equal to the sum of the partial pressure of the mixture of gasses.

$P_T=p_{H_2}+p_{H_2O}$

where,

$P_T$ = total partial pressure = 0.610 atm = 463.6 torr

conversion used : (1 atm = 760 torr)

$P_{H_2}$ = partial pressure of hydrogen gas = ?

$P_{H_2O}$ = partial pressure of water vapor = 18 torr

Now put all the given values is expression, we get the partial pressure of the hydrogen gas.

$463.6torr=p_{H_2}+18torr$

$p_{H_2}=445.6torr\approx 446torr$

Therefore, the partial pressure of $H_2$ gas is, 446 torr