chemistry partial Pressure

Question

a gas mixture used as an atmosphere for growing anaerobic bacteria contains 3.0% by mass of hydrogen and 97.0% by mass carbon dioxide, if the total pressure is 1.00 atm, what is the partial pressure of each gas in the mixture?

Answer 1

The partial pressure of each gas is related to the moles of each gas and total moles of all gases. Put another way, the mole fraction of a gas x total pressure = partial pressure of that gas. (see Dalton's law).

Let's assume we have 100 g of gas.

3.0 % is H₂, so that would be 3 g H₂ gas. 3 g H₂ x 1 mol/2 g = 1.5 moles H₂ gas

97.0 % is O₂, so that would be 97 g O₂ gas. 97 g O₂ x 1 mol/32 g = 3.03 moles O₂ gas

Total moles of gas = 4.53 moles

Mole fraction H₂ = 1.5/4.53 = 0.331

Mole fraction O₂ = 3.03/4.53 = 0.669

Partial pressure H₂ = 0.331 x 1.00 atm = 0.330 atm

Partial pressure O₂ = 0.669 x 1.00 atm = 0.669 atm