A mixture of 80.0 g of oxygen and 80.0 g of helium has a total pressure of 0.1800 atm. What is the partial pressure of each gas?

Partial pressure of O₂ =  0.0198 atm

Partial pressure of He = 0.1584 atm

Explanation:

Given data:

Mass of oxygen = 80.0 g

Mass of helium = 80.0 g

Total pressure = 0.1800 atm

Partial pressure of each gas = ?

Solution:

First of all we will calculate the number of moles.

Number of moles of oxygen:

Number of moles = mass/molar mass

Number of moles = 80.0 g/ 32 g/mol

Number of moles = 2.5 mol

Number of moles of helium:

Number of moles = mass/molar mass

Number of moles = 80.0 g/ 4 g/mol

Number of moles = 20 mol

Total number of moles = 20 mol + 2.5 mol = 22.5 mol

Mole fraction of O₂ = 2.5 mol/ 22.5 mol = 0.11

Mole fraction of He = 20 mol / 22.5 mol = 0.88

Partial pressure:

Partial pressure of O₂ =  0.11× 0.1800 atm = 0.0198 atm

Partial pressure of He = 0.88 × 0.1800 atm = 0.1584 atm