Solutions Question 116
Question: A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at 20°C are 440 mmHg for pentane and 120 mmHg for hexane. The mole fraction of pentane in the vapour phase would be [CBSE PMT 2005]
Options:
A) 0.549
B) 0.200
C) 0.786
D) 0.478
Show Answer
Answer:
Correct Answer: D
Solution:
$ P_{T}=P_p^{0}x_{p}+P_h^{0}x_{h} $ = $ 440\times \frac{1}{5}+120\times \frac{4}{5} $ = $ 88+96 $ = $ 184 $ ; $ P_p^{0}x_{p}=y_{p}P_{T} $ ; $ \frac{88}{184}=y_{p} $
$ y_{p}=0.478 $
