# How can I find partial pressure given moles?

Dec 16, 2014

Partial pressure is defined as the hypothetical pressure of a gas that is part of a mixture of gases that occupy a certain volume and a certain temperature, if that respective gas would occupy the same volum of the mixture, at the same temperature as the mixture.

Now, the mole fraction on an individual gas A that is a component of an ideal gas mixture can be expressed using either the moles of this component, or its partial pressure

${X}_{A} = {n}_{A} / {n}_{T O T A L} = {P}_{A} / {P}_{T O T A L}$, where

${n}_{A}$ represents the number of moles of gas A present in the mixture;
${n}_{T O T A L}$ represents the total number of moles present in the mixture;
${P}_{A}$ represents A's partial pressure;
${P}_{T O T A L}$ represents the total pressure of the gas mixture.

Therefore, a gas' partial pressure can be determined from its moles by knowing the total number of moles of the gaseous mixture and its total pressure

${P}_{A} = {n}_{A} / {N}_{T O T A L} \cdot {P}_{T O T A L}$