Question

A deep-sea diver uses a gas cylinder with a volume of 10.0 L and a content of 52.0 g of O2 and 32.1 g of He. How would you calculate the partial pressure of each gas and the total pressure if the temperature of the gas is 17 degrees C?

Answer 1

We use `"Dalton's Law of Partial Pressures...."` and get `P_"Total"=34.8*atm`.

Explanation:

`"Dalton's Law of Partial Pressures"` holds that in a gaseous mixture, the pressure exerted by a gas is the same as if it alone occupied the container. The total pressure is the sum of the individual partial pressures. And so here we must interrogate the molar quantities of each gas........

`"Moles of dioxygen"=(52.0*g)/(32.00*g*mol^-1)=1.625*mol`.

`"Moles of helium"=(52.0*g)/(4.00*g*mol^-1)=13.0*mol`.

`P_"Total"=(n_"Total"xxRxxT)/(V)=(14.625*molxx0.0821*(L*atm)/(K*mol)xx290*K)/(10*L)`

`=34.8*atm`

And ..................

`P_"dioxygen"=(1.625*mol)/(1.625*mol+13.0*mol)xx34.8*atm=3.87*atm`

`P_"helium"=(13.0*mol)/(1.625*mol+13.0*mol)xx34.8*atm=30.93*atm`

Why do they use helium instead of dinitrogen for this mix?