# What is meant by partial pressure of oxygen?

Feb 10, 2017

#### Answer:

In a gaseous mixture, the $\text{partial pressure}$ 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 $C$.........

${P}_{\text{Total}} = {P}_{A} + {P}_{B} + {P}_{C} \ldots \ldots \ldots \ldots \ldots \ldots .$

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

${P}_{\text{Total}} = \frac{{n}_{A} R T}{V} + \frac{{n}_{B} R T}{V} + \frac{{n}_{C} R T}{V} \ldots \ldots \ldots \ldots \ldots \ldots .$

${P}_{\text{Total}} = \frac{R T}{V} \left\{{n}_{A} + {n}_{B} + {n}_{C} \ldots \ldots \ldots \ldots . .\right\}$

and clearly, ${P}_{A} = {P}_{A} / {P}_{\text{Total}} = {n}_{A} / \left\{{n}_{A} + {n}_{B} + {n}_{C} \ldots \ldots \ldots \ldots . .\right\}$

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

The air we breathe now is approx. $1 \cdot a t m$ pressure (unless you live in Denver).

And thus ${P}_{\text{Total"=P_"dioxygen"+P_"dinitrogen"+P_"other gases}}$

And so ${P}_{\text{dioxygen}} = 0.20 \cdot a t m$. ${P}_{\text{dinitrogen}} = 0.78 \cdot a t m$

${P}_{\text{dinitrogen"+P_"dioxygen"~=1*"atm}}$