Which one of the following pairs of solution can we expect to be isotonic at the same temperature? — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Solutions are isotonic if they exert the same osmotic pressure ($i \times C$). $\text{Na}_2\text{SO}_4$ gives 3 ions ($i \approx 3$, effective conc = 0.3 M). $\text{Ca(NO}_3\text{)}_2$ also gives 3 ions ($i \approx 3$, effective conc = 0.3 M). They match perfectly. Therefore, correct answer is D.