What is meant by partial pressure of oxygen?

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Answer 1 · 2017-02-10T08:02:33

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

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 $P_"dioxygen"=0.20*atm$ . $P_"dinitrogen"=0.78*atm$

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