Question

A gaseous mixture at `780*mm*Hg` pressure contains carbon dioxide, and dioxygen. If `P_(CO_2)=560*mm*Hg`, what is `P_(O_2)`?

Answer 1

Well it is nominally `220*mm*Hg`.

Explanation:

`P_"Total"=P_(CO_2)+P_(O_2)`

`P_(O_2)=P_"Total"-P_(CO_2)=(780-560)*mm*Hg.`

Dalton's Law of partial pressures states that in a gaseous mixture, the partial pressure exerted by a component is the same as the pressure if it alone occupied the container. The total pressure is the sum of the individual partial pressures.

And thus for atmospheric pressure, we can state that.........

`P_"total"=P_(N_2)+P_(O_2)+P_("other gases")=1*atm.`

In practice, you DO NOT use a mercury column to measure a pressure OVER `1*atm`. Try to do this and you will likely get mercury all over the lab.