A mixture of helium and neon gases, at a total pressure of 851 mm Hg, contains 0.666 grams of helium and 2.55 grams of neon. What is the partial pressure of each gas in the mixture?

Question

A mixture of helium and neon gases, at a total pressure of 851 mm Hg, contains 0.666 grams of helium and 2.55 grams of neon. What is the partial pressure of each gas in the mixture?

P_He = _____ mm Hg

P_Ne = _____ mm Hg

Answer 1

You should know that the partial pressure of a gas in a mixture is equal to the mole fraction of that gas times the total pressure. We know the total pressure is 851 mm Hg. So, all we need to do is find the mole fractions of He and Ne and then we can calculate the partial pressures of each.

moles He =0.666 g He x 1 mol He / 4 g = 0.1665 mols He

moles Ne = 2.55 g Ne x 1 mol Ne / 20.2 g = 0.1262 mols Ne

Total mols = 0.1665 + 0.1262 = 0.2927 mols

Mole fraction He = 0.1665 / 0.2927 = 0.569

Partial pressure He = 0.569 x 851 mm Hg = 484 mm Hg He

Mole fraction Ne = 0.1262 / 0. 2927 = 0.431

Partial pressure Ne = 0.431 x 851 mm Hg = 367 mm Hg Ne