Question

What pressure IN `"kilopascals"` is exerted by the DRY gas if it is has been collected over water at `75` `""^@C`, and the total pressure is `3.41*atm`?

Answer 1

You need to quote the `"saturated vapour pressure"` for an accurate answer.

Explanation:

The pressure exerted by gases ABOVE an aqueous phase is equal to the SUM of the pressure of the individual gases, and the so-called `"saturated vapour pressure"` that the water molecules exert. That this must be considered in the problem is indicated by the specific wording; they specify a `"dry gas"`.

At `75` `""^@C`, `"= SVP = 0.3806"*"atm"`. These data are taken from this site. What is `"SVP"` at `100` `""^@C`?

And so `P_"measured"=P_"gas"+P_"SVP"`, and............

`P_"Gas"=P_"measured"-P_"SVP"=(3.41-0.3806)*atm=3.029*atm`.

And so, since `1*atm-=101.3*kPa`, then...........

`P_"gas"=3.029*atmxx101.3*kPa*atm^-1~=303*kPa`.