What is the partial pressure of gases?

1 Answer
anor277
Jul 19, 2018

In a gaseous mixture, the partial pressure is the pressure exerted by a component gas if it ALONE occupied the container.

Explanation:

The total pressure is the SUM of the individual partial pressures. Ans so the air we breathe (at approx. #1*atm#) COULD be expressed as #P_"ambient"=underbrace(P_"dioxygen"+P_"dinitrogen"+P_"other gases")_"0.21(atm)+0.78(atm)+0.1(atm)"#.

So in a gaseous mixture:

#P_"Total"# #=# #P_1 + P_2 + P_3+............P_n#

Where #P_i# is the partial pressure of a component. But we can assume ideality, and thus,

#P_1=(n_1RT)/V#, etc. since #V# and #T# are common to all the gases.

Since the total pressure is the sum of the partial pressures,

#P_"Total"=(n_1 + n_2........+n_n)(RT)/V#

And #P_1# #=# #n_1/(n_1+n_2+n_3+....n_n)xx(RT)/V#

And so the partial pressure of a component is proportional to the mole fraction of that component. The law of course presupposes that the individual gases do not react with each other.

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