A mixture of hydrogen and oxygen contains 40% hydrogen by mass when the pressure is 2.2 bar. The partial pressure of hydrogen is bar. (Nearest Integer).

Let the mass of mixture be 100g
$\Rightarrow$ mass of hydrogen is 40g
$\Rightarrow$ mass of oxygen is 60g
${\mathrm{P}}_{\mathrm{T}} ={\mathrm{P}}_{{\mathrm{H}}_2}+{\mathrm{P}}_{{\mathrm{O}}_2}$
$$\begin{gathered} \begin{array}{l}{\mathrm{P}}_{{\mathrm{H}}_{\mathrm{T}}}= {\mathrm{x}}_{{\mathrm{H}}_2}-{\mathrm{P}}_{\mathrm{T}} \\ \because {\mathrm{M}}_{{\mathrm{H}}_2}=\frac{40}{2}\mathrm{mol}=20\mathrm{mol} {\mathrm{\eta }}_{{\mathrm{O}}_2}=\frac{60}{32}=1.875\\ \Rightarrow {\mathrm{x}}_{{\mathrm{H}}_2}=\frac{20}{20+1.875}=0.91\\ {\text{ ∴ P}}_{{\mathrm{H}}_2}=0.91\times 2.2\text{ bar }=2.011\text{ bar }\\ \end{array} \end{gathered}$$