States of Matter - Result Question 40
40. Equal weights of methane and oxygen are mixed in an empty container at $25^{\circ} C$. The dfraction of the total pressure exerted by oxygen is
(1981,1 M)
(a) $\dfrac{1}{3}$
(b) $\dfrac{1}{2}$
(c) $\dfrac{2}{3}$
(d) $\dfrac{1}{3} \times \dfrac{273}{298}$
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Answer:
Correct Answer: 40. (a)
Solution:
If $x g$ of both oxygen and methane are mixed then :
$ \begin{aligned} \text { Mole of oxygen } & =\dfrac{x}{32} \\ \text { Mole of methane } & =\dfrac{x}{16} \end{aligned} $
$ \Rightarrow \quad \text { Mole fraction of oxygen }=\dfrac{\dfrac{x}{32}}{\dfrac{x}{32}+\dfrac{x}{16}}=\dfrac{1}{3} $
According to law of partial pressure
Partial pressure of oxygen $\left(p _{O _2}\right)=$ Mole fraction $\times$ Total pressure
$ \Rightarrow \quad \dfrac{p _{O _2}}{p}=\dfrac{1}{3} $
BETA
