Question

400 mL of hydrogen gas at a pressure of 300 mm $Hg$ and 200 mL of hydrogen chloride gas at a pressure of 600 mm $Hg$ are mixed in a one litre evacuated flask. Calculate the resulting pressure (in $\text{mm Hg}$) of the mixture at the same temperature.

Answer 1

Mole after mixing = Mole before mixing
$n_T=n_{H_2}+n_{HCl}$ (where, $n_T$ = total mole of mixture)
From the ideal gas equation,
$PV=nRT$
$n=\frac{RT}{PV}$
Since, $n_T=n_{H_2}+n_{HCl}$
So
$P_T{V}_T/RT=P_{H_2}{V}_{H_2}/RT+P_{HCl}{V}_{HCl}/RT$
$P_T\times 1000=300\times 400+600\times 200$
$P_T=240\text{mm Hg}$