Question

Equal weights of methane and oxygen are mixed in an empty container at ${25}^{o}C.$ The fraction of the total pressure exerted by oxygen is
(IIT-JEE, 1981)

• A. $\frac{1}{3}$
• B. $\frac{1}{2}$
• C. $\frac{2}{3}$
• D. $\frac{1}{3}\times \frac{273}{298}$

Answer 1

The correct option is A $\frac{1}{3}$

Let 32 g of each be present.
Moles of $O_2=\frac{32}{32}=1$
Moles of $C{H}_4=\frac{32}{16}=2$
Mole fraction of $O_2=\frac{1}{1+2}=\frac{1}{3}$ which is same as the fraction of pressure.