Question

Equal masses of methane and oxygen are mixed in an empty container at ${25}^{o}C$. The fraction of total pressure exerted by oxygen is:

• A. $1/3$
• B. $1/2$
• C. $2/3$
• D. $\frac{1}{3}\times \frac{273}{308}$

Answer 1

Answer: (A)

$1/3$

If $xg$ of both oxygen and $C{H}_4$ are mixed then,

Moles of $O_2=\frac{x}{32}$

Moles of $C{H}_4=\frac{x}{16}$

$\therefore$ Mole fraction of $O_2=\frac{\frac{x}{32}}{\frac{x}{32}+\frac{x}{16}}=\frac{1}{3}$

Partial pressure exerted by $O_2=\frac{\text{Mole fraction}}{\text{Total pressure}}=\frac{\frac{1}{3}\times P}{P}=\frac{1}{3}$