Question

A gaseous mixture of O2 and N2 contains 35.4 % nitrogen by mass. What is the partial pressure of oxygen in the mixture if the total pressure is 0.918 atm

Answer 1

0.565 atm

Step-by-step explanation:

Let's assume we have 100 g of the gas. We'd then have 35.4 g of N₂ and (100 - 35.4) 64.6 g of O₂.

Now we convert those masses into moles, using their respective molar masses:

• 35.4 g N₂ ÷ 28 g/mol = 1.26 mol N₂

• 64.6 g O₂ ÷ 32 g/mol = 2.02 mol O₂

Then we calculate the molar fraction of O₂:

• Molar Fraction O₂ =
  `(2.02mol)/(1.26mol+2.02mol)` = 0.616

Finally we calculate the partial pressure of O₂:

• Partial P = Total P * Molar Fraction = 0.565 atm