Question

A gas mixture with a total pressure of 755 mmHg contains each of the following gases at the indicated partial pressures: 120 mmHg CO2CO2, 234 mmHg Ar, and 190 mmHg O2. The mixture also contains helium gas.

What is the partial pressure of the helium gas?

Express your answer in millimeters of mercury.

Answer 1

According to the Dalton's law of partial pressure, the total pressure of the gas mixture is the sum of the partial pressure of all of the gases in the mixture.

Thus, here,

total pressure = partial pressure of CO₂ + partial pressure of Ar + partial pressure of O₂ + partial pressure of He

or, 755 mmHg = 120 mmHg + 234 mmHg + 190 mmHg + partial pressure of He

or, partial pressure of He = (755 - 120 - 234 - 190) mmHg

= 211 mmHg

Hence, the partial pressure of the helium gas = 211 mmHg