Question

x% (w/v) solution of urea is isotonic with 4% (w/v) solution of non-volatile solute of molar mass 120 g mol-1. The value of x is

• A. 2
• B. 4
• C. 3
• D. 5

Hint:

Use isotonicity condition: $\dfrac{w}{M}$ ratio of both solutions must be equal for same volume.

Answer 1

The Correct Option is A

$\dfrac{x}{60} = \dfrac{4}{120} \Rightarrow x = \dfrac{60 \times 4}{120} = 2$
(urea molar mass = 60, given solute = 120)