Question

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

• A. $350$
• B. $300$
• C. $700$
• D. $360$

Answer 1

Answer: (A)

$350$

Answer 2

Let the vapour pressure of pure ethyl alcohol be P, According to Raoult?s law $P=\frac{290-80}{0.6}=350\,mm\,Hg$