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

Answer: (A)

$0.8$

Answer 2

Let the total mass of the mixture be $100 \,g$ Mass of $H_{2}$ =$\frac{20}{100}\times100=20 \,g$ No. of moles of $H_{2}$ = $\frac{20}{2}=10$ moles Mass o f $O_{2}$ = $100-20=80 \,g$ No. of moles of $O_{2}$ = $\frac{80}{32} = 2.5$ moles 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 mixture = 1 bar $\therefore$ $\quad$ Partial pressure of $H_{2}$ in the mixture, $p_{H_2}$ =Mole fraction \times Total pressure =$0.8\times1=0.8$ bar