Question

At constant temperature and volume, a `0.2*mol` quantity of helium gas exerts a pressure of `22.7*kPa`. HALF this molar quantity of oxygen gas is injected, what is `P_"Total"`?

`A.` `34.05*kPa;`
`B.` `69.10*kPa;`
`C.` `25.05*kPa;`
`D.` `"Impossible to determine."`

Answer 1

`"Option A"`

Explanation:

`"Dalton's Law of Partial Pressures"` states that in a gaseous mixture, the partial pressure, `P_1`, exerted by a gaseous component is the same as the pressure it would exert if it ALONE occupied the container. The total pressure, `P_"Total"`, is the sum of the individual partial pressures:

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

Here, `0.2*mol` quantity of helium gas exerts a `22.7*kPa` pressure, so if we inject a `0.1*mol` quantity of dioxygen gas it will exert a proportional pressure, i.e. proportional to its molar quantity, a pressure of `11.35*kPa`. `P_"Total"=(22.7+11.35)*kPa=A`, as required.....

Happy?

Why doesn't the helium gas react with the dioxygen gas? Dioxygen gas is fiercely reactive.