Q39 / 120 · JEE Main 2007 · Chemistry

A mixture of ethyl alcohol and propyl alcohol has a vapour pressure of $290 \mathrm{~mm}$ at $300 \mathrm{~K}$. The vapour pressure of propyl alcohol is $200 \mathrm{~mm}$. If the mole fraction of ethyl alcohol is $0.6$, its vapour pressure (in $\mathrm{mm}$) at the same temperature will be

  • Correct answer
    A
    $350$
  • B
    $300$
  • C
    $700$
  • D
    $360$

Solution

Let the vapour pressure of pure ethyl alcohol be $\mathrm{P}$, According to Raoult's law $\begin{aligned} & 290=200 \times 0.4+\mathrm{P} \times 0.6 \\ & \mathrm{P}=\frac{290-80}{0.6}=350 \mathrm{~mm} \mathrm{~Hg} \end{aligned}$ Hence, (A) is correct.

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

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