Chapter 5, Problem 127AE

Interpretation Introduction

Interpretation: The partial pressures of each gas in the given sample containing mixture of $\text{50}\%$ helium and $50\%$ xenon by mass are needed to be determined, it the total pressure of sample is given as $\text{600}\text{torr}$.

Concept introduction:

• Partial pressure of a gas in a mixture of gases is the pressure of that gas when it alone.

Partial pressure of a gas in terms of its mole fraction and total pressure is,

` ${\text{P}}_{\text{A}}\text{=}{\text{χ}}_{\text{A}}\text{×}{\text{P}}_{\text{TOTAL}}$

• Mole fraction of a molecule in a mixture is the ratio of number of moles of particular molecule to the sum of number of moles of all molecules in the mixture.

  Equation for mole fraction of a molecule in a mixture of two molecules (A and B) is,

$\text{molecule}\text{fraction}\text{of}\text{A,}\text{(}{\text{χ}}_{\text{A}}\text{) }\text{=}\frac{\text{numbers}\text{of moles of}\text{A}{\text{(n}}_{\text{A}}\text{)}}{\text{numbers}\text{of moles of}\text{A}{\text{(n}}_{\text{A}}\text{)}\text{+}\text{numbers}\text{of moles of}\text{B}{\text{(n}}_{\text{B}}\text{)}}$

• Number of moles of a substance from its given mass is,

$\text{Number of moles}\text{=}\frac{\text{Given}\text{mass}}{\text{Molecular}\text{mass}}$

• Total pressure of a mixture of gases is the sum of individual partial pressures of constituted gases.

To determine: the partial pressure of each gas in the given mixture of $\text{50}\%$ helium and $50\%$ xenon by mass.