[mark1950]

4.0 dm3 of nitrogen at a pressure of 400 kNm-2 and 1.0dm3 of argon at a pressure of 200kNm-2 are introduced into a container of volume 2.0dm3.

Calculate the partial pressure of nitrogen.

The solution given was,

From Boyle's law, the partial pressure of nitrogen
= 400kNm-2 x 4.0/2.0
= 800kNm-2

The thing that I don't understand is, why do they use Boyle's law? The definition of Boyle's law has nothing to do with partial pressure. I thought that Boyle's law is about comparing the pressure and Volume of gases before and after. Thanks.

[Borek]

Final pressure is sum of partial pressures and they can be treated independently. Presence of argon doesn't change partial pressure of nitrogen, it only changes total pressure.

That's not exactly true, as it holds only for ideal gases.