Q. 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
Explanation
(a)
According to Raoult’s law
$\ p = \ p_{A}^{\circ}X_{A} + p_{B}^{\circ}X_{B}\$
$\ \ \ = \ 290 = 200 \times \ 0.4 + p_{B}^{\circ} \times 0.6\ \ \$
$\ p_{B}^{\circ} = \ 350$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.