Question

A gas mixture with a total pressure of 755 mmHgcontains each of the following gases at the indicated partial pressures: CO2, 265 mmHg ; Ar, 132 mmHg ; and O2, 174 mmHg . The mixture also contains helium gas.

a) What is the partial pressure of the helium gas?

b) What mass of helium gas is present in a 15.0-L sample of this mixture at 283 K ?

Answer 1

Dalton's law of partial pressures: The total pressure of a mixture of gases is just the sum of the pressures that each gas would exert if it where present alone.

The total pressure of the mixture is 755 mm Hg

The partial pressure of a gas in a mixture of gases can be expressed as: where is the mole fraction of the component A in the mixture.

For the Helium gas or

Accordint to the ideal gas equation

or

  

From mole fraction definition:

MW of Helium = 4 g/mol

(4 g/mol)*(0.156 mol) = 0.624 g of helium