Q15 / 120 · JEE Main 2007 · Chemistry

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

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

Solution

Let the mass of methane and oxygen is $w$ $\begin{aligned} & \text { mole fraction of oxygen }=\frac{\frac{w}{32}}{\frac{w}{32}+\frac{w}{16}} \\ & =\frac{\frac{1}{32}}{\frac{1}{32}+\frac{1}{16}}=\frac{\frac{1}{32}}{\frac{3}{32}}=\frac{1}{3} \end{aligned}$ Let the total pressure be $\mathrm{P}$ The pressure exerted by oxygen (partial pressure) $=\mathrm{X}_{\mathrm{O}_2} \times \mathrm{P}_{\text {total }}$ $\Rightarrow \mathrm{P} \times \frac{1}{3}$ Hence, (C) is correct.

Hence, the correct answer is option: 'C'.

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