Question

What is meant by partial pressure of oxygen?

Answer 1

In a gaseous mixture, the `"partial pressure"` of a gas is the pressure that gas would exert if it ALONE occupied the container.

Explanation:

The total pressure is the sum of the individual partial pressures.

And so when we have a gaseous mixture of several gases, `A`, `B`, and `C`.........

`P_"Total"=P_A+P_B+P_C...................`

And to assess `P`, we may simply use the ideal gas equation:

`P_"Total"= (n_ART)/V+(n_BRT)/V+(n_CRT)/V...................`

`P_"Total"=(RT)/V{n_A+n_B+n_C..............}`

and clearly, `P_A=P_A/P_"Total"=n_A/{n_A+n_B+n_C..............}`

And thus the partial pressure of a component is proportional to the mole fraction of that component.

The air we breathe now is approx. `1*atm` pressure (unless you live in Denver).

And thus `P_"Total"=P_"dioxygen"+P_"dinitrogen"+P_"other gases"`

And so `P_"dioxygen"=0.20*atm`. `P_"dinitrogen"=0.78*atm`

`P_"dinitrogen"+P_"dioxygen"~=1*"atm"`