Question

What is the partial pressure of gases?

Answer 1

In a gaseous mixture, the partial pressure is the pressure exerted by a component gas if it ALONE occupied the container.

Explanation:

The total pressure is the SUM of the individual partial pressures. Ans so the air we breathe (at approx. `1*atm`) COULD be expressed as `P_"ambient"=underbrace(P_"dioxygen"+P_"dinitrogen"+P_"other gases")_"0.21(atm)+0.78(atm)+0.1(atm)"`.

So in a gaseous mixture:

`P_"Total"` `=` `P_1 + P_2 + P_3+............P_n`

Where `P_i` is the partial pressure of a component. But we can assume ideality, and thus,

`P_1=(n_1RT)/V`, etc. since `V` and `T` are common to all the gases.

Since the total pressure is the sum of the partial pressures,

`P_"Total"=(n_1 + n_2........+n_n)(RT)/V`

And `P_1` `=` `n_1/(n_1+n_2+n_3+....n_n)xx(RT)/V`

And so the partial pressure of a component is proportional to the mole fraction of that component. The law of course presupposes that the individual gases do not react with each other.