How can I find partial pressure given moles?

1 Answer
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_(TOTAL) = P_A/P_(TOTAL)#, where

#n_A# represents the number of moles of gas A present in the mixture;
#n_(TOTAL)# represents the total number of moles present in the mixture;
#P_A# represents A's partial pressure;
#P_(TOTAL)# 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_(TOTAL) * P_(TOTAL)#