Question

A $0.1molar$ solution of $NaCl$ is found to be isotonic with $1\%$ urea solution. Calculate
(a) Van't Hoff factor
(b)Degree of dissociation of sodium chloride.
Assume density of $1\%$ urea equal to $1gc{m}^{-3}$.

• A. (a)$1.667,$ (b)$0.667$
• B. (a)$1.82,$ (b)$0.69$
• C. (a)$2.01,$ (b)$0.78$
• D. (a)$2.12,$ (b)$0.94$

Answer 1

The correct option is A (a)$1.667,$ (b)$0.667$

$NaCl(1-x)$ dissociates into $N{a}^{+}\left(x\right)$ and $C{l}^{-}\left(x\right)$

Total concentration in solution $=c(1+x)=0.1M(1+x)$

Osmotic pressure of $NaCl$ solution $=0.1M(1+x)RT$

Osmotic pressure of urea solution $=\frac{\left(1/60\right)mol}{0.1L}RT$

since solutions are isotonic, therefore, $1+x=1.667$

(b) Degree of dissociation $=x=0.667$