Q23 / 160 · TS EAMCET 2019 (03 May Shift 2) · Chemistry

If $0.1 M$ solution of $NaCl$ is isotonic with $1.1 w %$ urea solution, the degree of ionisation of $NaCl$ is (Molar masses of urea and $NaCl$ are $60$ and $58.5 g {mol}^{- 1}$ , respectively.)

Solution

Isotonic solution: Two solutions having the same osmotic pressure across a semipermeable membrane is referred to as an isotonic solution.

$π_{NaCl} = π_{Urea} = \frac{nRT}{V} i \times 0.1 \times RT = \frac{1.1}{60 \times 0.1} \times RT \Rightarrow i = 1.83$

Also, we know,

$α = \frac{i - 1}{n - 1} = \frac{1.83 - 1}{2 - 1} = 0.83$

Hence, the correct answer is option: 'B'.