Q. 5 moles of liquid X and 10 moles of liquid Y make a solution having a vapour pressure of 70 torr. The vapour pressures of pure X and Y are 63 torr and 78 torr respectively. Which of the following is true regarding the described solution?
A) The solution shows positive deviation.
B) The solution shows negative deviation.
C) The solution is ideal.
D) The solution has volume greater than the sum of individual volumes.
Explanation
[Solution by Claude - not from source] Ideal vapour pressure $=\frac13(63)+\frac23(78)=21+52=73$ torr. Observed $70<73$, so negative deviation (and volume decreases on mixing). Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.