Solutions Question 128
Question: 60 gm of Urea (Mol. wt 60) was dissolved in 9.9 moles, of water. If the vapour pressure of pure water is $ P_{o} $ , the vapour pressure of solution is [DCE 2000]
Options:
A) 0.10 $ P_{o} $
B) 1.10 $ P_{o} $
C) 0.90 $ P_{o} $
D) 0.99 $ P_{o} $
Show Answer
Answer:
Correct Answer: C
Solution:
$ \frac{P^{0}-P_{s}}{P^{0}}=\frac{n}{N}\Rightarrow \frac{P^{0}-P_{s}}{P^{0}}=\frac{1}{9.9}\Rightarrow 9.9P^{0}-9.9P_{s}=P^{0} $
$ 8.9P^{0}=9.9P_{s}\Rightarrow P_{s}=\frac{8.9}{9.9}P^{0}\approx 0.90P^{0} $
