Solutions Question 312
Question: Vapour pressure (in torr) of an ideal solution of two liquids A and B is given by: $ P=52X_{A}+114 $ where $ X_{A} $ is the mole fraction of A in the mixture. The vapour pressure (in torr) of equimolar mixture of the two liquids will be:
Options:
A) 166
B) 83
C) 140
D) 280
Show Answer
Answer:
Correct Answer: C
Solution:
Total V.P., $ P=P_A^{0}X_{A}+P_B^{0}X_{B}=P_A^{0}X_{A}+P_B^{0}(1-X_{A}) $
$ =( P_A^{0}-P_B^{0} )X_{A}+P_B^{0} $ Thus, $ P_{B}{}^\circ =114,torr;P_A^{0}-P_B^{0}=52 $ or $ P_A^{0}=166torr $ Hence $ P=166\times \frac{1}{2}+114\times \frac{1}{2}=140torr $
