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Q.
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 $ W _{ H _2}=40 g \Rightarrow n _{ H _2}=\frac{40}{2}=20$
$W _{ O _2}=60 g \Rightarrow n _{ O _2}=\frac{60}{32}=\frac{15}{8}$
$ P _{ H _2}=\left(\frac{20}{20+\frac{15}{8}}\right) \times 2.2$
$ =\frac{20}{20+1.875} \times 2.2$
$ =\frac{20}{21.875} \times 2.2$
$=2.0114 $
$ \simeq 2.01 \,bar$