Aqueous solutions of and are isotonic. The percentage dissociation of is — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Isotonic means $i_1 C_1 = i_2 C_2$. Let $i$ be the factor for $\text{Na}_2\text{SO}_4$. $i \times 0.004 = 1 \times 0.01 \Rightarrow i = 2.5$. For $\text{Na}_2\text{SO}_4 \rightarrow 2\text{Na}^+ + \text{SO}_4^{2-}$, $n = 3$. $i = 1 + (n-1)\alpha \Rightarrow 2.5 = 1 + 2\alpha \Rightarrow 2\alpha = 1.5 \Rightarrow \alpha = 0.75$ or 75%. Therefore, correct answer is C.