Question

A mixture of dihydrogen and dioxygen at one bar pressure contains $20$% by weight of dihydrogen. What would be the partial pressure of dihydrogen in bar?

• A. $0.8$
• B. $1.8$
• C. $2.8$
• D. $3.0$

Answer 1

The correct option is A $0.8$

Let the total mass of the mixture be $100g$
Mass of $H_2=\frac{20}{100}\times 100=20g$
No. of moles of $H_2=\frac{20}{2}=10moles$
Mass of $O_2=100-20=80g$
No. of moles of $O_2=\frac{80}{32}=2.5moles$
Total number of moles of $H_2$ and $O_2=10+2.5=12.5$
Mole fraction of $H_2=\frac{10}{12.5}=0.8$
Total pressure of mixtures $=1bar$
$\therefore$ Partial pressure of $H_2$ is the mixture, $p_{H_2}$
$=Molefraction\times Totalpressure=0.8\times 1=0.8bar$.