Question

A gaseous mixture of O2 and N2 contains 33.8 % nitrogen by mass. What is the partial pressure of oxygen in the mixture if the total pressure is 505 mmHg ?

Answer 1

Solution :

Let us consider, we have 100 g of gaseous mixture of N₂ and O₂.

Amount of Nitrogen in mixture = 33.8 g

Amount of Oxygen in the mixture = 66.2 g

Molar mass of Nitrogen = 28 g/mol

Molar mass of Oxygen = 32 g/mol

Therefore, number of moles of N₂ = Given mass / molar mass = 33.8 / 28 = 1.207 moles

Number of moles of O₂ = Given mass / Molar mass = 66.2 / 32 = 2.07 moles

Mole fraction of Oxygen = 2.07 / ( 1.207 + 2.07 ) = 0.632

Partial pressure is given by ;

Partial pressure = Mole fraction total pressure

So, Partial pressure of Oxygen = 0.632 505 = 319 mmHg

Therefore, partial pressure of oxygen in the mixture is = 319 mmHg