Question

The pressure of a mixture of $H_2$ and $O_2$ enclosed in a vessel having molar ratio $1:4$, is one atmosphere. What would be the partial pressure of dioxygen?
(Given: $1\text{atm}=101325{\text{Nm}}^{-2}$)

• A. $0.8\times {10}^5\text{atm}$
• B. $0.008\text{Nm}{}^{-2}$
• C. $8.1\times {10}^4\text{Nm}{}^{-2}$
• D. $0.25\text{atm}$

Answer 1

The correct option is C $8.1\times {10}^4\text{Nm}{}^{-2}$

Let the number of moles of dihydrogen and dioxygen be $1$ and $4$ respectively.
Mole fraction of $O_2$ = $\frac{\text{number of moles of dioxygen}}{\text{total number of moles in the mixture}}=\frac{4}{5}$

Total pressure = $1\text{atm}$

$\text{Partial pressure of dioxygen}=\text{Mole fraction}\times \text{Total pressure}$
$=\frac{4}{5}\times 1\text{atm =0.8 atm}=0.8\times 101325{\text{Nm}}^{-2}=81060{\text{Nm}}^{-2}=8.1\times {10}^4\text{Nm}{}^{-2}$