Solutions Question 310
Question: Vapour pressure of chloroform $ (CHCl_3) $ and dichloromethane $ (CH_2Cl_2) $ at $ 25{}^\circ $ C are 200 mm Hg and 41.5 mm Hg respectively. Vapour pressure of the solution obtained by mixing 25.5 g of $ CHCl_3 $ and 40 g of $ CH_2Cl_2 $ at the same temperature will be: (Molecular mass of $ CHCl_3=119.5u $ and molecular mass of $ CH_2Cl_2=85u $ ).
Options:
A) 90.92 mm Hg
B) 115.0 mm Hg
C) 147.9 mm Hg
D) 285.5 mm Hg
Show Answer
Answer:
Correct Answer: A
Solution:
$ ^{n}CHCl_3=\frac{25.5}{119.5}=0.213 $
$ ^{n}CH_2Cl_2=\frac{40}{85}=0.47 $
$ P_{T}=P_A^{0}X_{A}+P_B^{0}X_{B} $
$ =200\times \frac{0.213}{0.683}+41.5\times \frac{0.47}{0.683} $
$ =62.37+28.55=90.92 $
