What is the equation for Dalton's law of partial pressure?

1 Answer
anor277
Dec 23, 2016

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

Explanation:

In a gaseous mixture, the partial pressure exerted by a component, is the same as the pressure it would exert if it ALONE occupied the container. The total pressure is the sum of the individual pressures. The mole fraction of a component gas is proportional to the partial pressure.

Clearly, the total number of moles of gas is..........

#n_"Total"# #=# #n_1+n_2+.......n_n#

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

But given ideality, then #P_i=(n_iRT)/V#

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

And #P_i# #=# #(n_iRT)/V# #=# #n_i/(n_1+n_2+.......n_n)xxP_"Total"#

Again, #P_"Total"# #=(n_1+n_2+n_3.........+n_n)(RT)/V#

It is worthwhile spending a bit of time on the equation, and checking problems where you use it .

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