‘x’ g of a non-electrolytic compound () is dissolved in 1 l of 0.05 M NaCl aqueous solution. The osm — Solutions and Colligative Properties Chemistry Question
Question
‘x’ g of a non-electrolytic compound ($M=200$) is dissolved in 1 l of 0.05 M NaCl aqueous solution. The osmotic pressure of this solution is found to be 4.92 atm at $27^\circ\text{C}$. Assume complete dissociation of NaCl and ideal behaviour for solution. The value of ‘x’ is ($R = 0.082 \text{ l-atm mol}^{-1}\text{K}^{-1}$)
💡 Solution & Explanation
NaCl dissociates completely into 2 ions ($i=2$), contributing an effective concentration of $2 \times 0.05 = 0.10 \text{ M}$. Let the non-electrolyte contribute $C = x / 200 \text{ M}$. The total effective concentration $C_{total} = 0.10 + x/200$. Using $\pi = C_{total} R T \implies 4.92 = (0.10 + x/200) \times 0.082 \times 300 = (0.10 + x/200) \times 24.6$. Solving for the concentration: $0.10 + x/200 = 4.92 / 24.6 = 0.20 \implies x/200 = 0.10 \implies x = 20$. Therefore, correct answer is 0020.