Solutions Question 358
Question: $ {\pi_1},{\pi_2},{\pi_3} $ and $ {\pi_4} $ atm are the osmotic pressures of 5% (mass/volume) solutions of urea, fructose, sucrose and $ KCl $ respectively at certain temperature. The correct order of their magnitudes is:
Options:
A) $ {\pi_1}>{\pi_4}>{\pi_2}>{\pi_3} $
B) $ {\pi_1}>{\pi_4}>{\pi_2}>{\pi_3} $
C) $ {\pi_4}>{\pi_1}>{\pi_2}>{\pi_3} $
D) $ {\pi_4}>{\pi_1}>{\pi_3}>{\pi_2} $
Show Answer
Answer:
Correct Answer: C
Solution:
Moles of urea $ =\frac{5}{60}; $ moles of fructose $ =\frac{5}{180}; $
$ C_{urea}=\frac{0.08\times 1000}{100}\Rightarrow 0.833 $ moles of sucrose $ =\frac{5}{342}; $
$ C_{sucrose}=0.0146\times \frac{1000}{100}=0.146 $ moles of $ KCl $ (effective) $ =2\times \frac{5}{74.5}=\frac{5}{37.25};\frac{0.134\times 1000}{100}=1.34 $
$ \pi \propto C $ this order is $ {\pi_4}>{\pi_1}>{\pi_2}>{\pi_3} $
