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Question: Answered & Verified by Expert
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
ChemistrySolutionsJEE MainJEE Main 2007
Options:
  • A
    $350$
  • B
    $300$
  • C
    $700$
  • D
    $360$
Solution:
1528 Upvotes Verified Answer
The correct answer is:
$350$
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.

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