If 0.1 molal aqueous solution of sodium bromide freezes at at one atmospheric pressure, the per cent — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

$\Delta T_f = 0.3348$. $i = \Delta T_f / (K_f \times m) = 0.3348 / (1.86 \times 0.1) = 0.3348 / 0.186 = 1.8$. NaBr dissociates into 2 ions ($n=2$). $i = 1 + \alpha \Rightarrow 1.8 = 1 + \alpha \Rightarrow \alpha = 0.8$, which corresponds to 80% dissociation. Therefore, correct answer is B.