Question

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

Answer 1

`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 .