Calculate pressure using Dalton's law of partial pressures.

Question

A gas mixture is made up of H₂ (0.581 g), He (1.15 g), and Ne (7.02 g). The mixture has a volume of 33.1 L at 80 °C. Calculate the partial pressure of each gas in the mixture and the total pressure of the gas mixture.

P_H2 = ______ atm

P_He = ______ atm

P_Ne = ______ atm

P_total = ______ atm

Answer 1

The partial pressure of each gas will be the total pressure times the mole fraction of each gas.

moles H₂ = 0.581 g H₂ x 1 mol H₂ / 2.02 g = 0.288 mols H₂. mole fraction H2 = 0.288/0.924 = 0.312

moles He = 1.15 g He x 1 mol He / 4.00 g = 0.288 mols He. mole fraction He = 0.288/0.924 = 0.312

moles Ne = 7.02 g Ne x 1 mol Ne / 20.2 g = 0.348 mols Ne. mole fraction Ne = 0.348/0.924 = 0.377

Total moles of gas = 0.924 mols

Use the ideal gas law to find the total pressure

PV = nRT

P = pressure = ?

V = volume in L = 33.1 L

n = mols = 0.348 mols

R = gas constant = 0.0921 Latm/Kmol

T = temp in Kelvin = 80C + 273 = 353K

Solving for P

P = nRT/V = (0.348)(0.0821)(353) / 33.1

P = 0.305 atm = TOTAL PRESSURE

Solving for partial pressures:

P_H2 = 0.305 atm x 0.312 = 0.0952 atm

P_He = 0.305 atm x 0.312 = 0.0952 atm

P_Ne = 0.305 x 0.377 = 0.115 atm