Match the following if the molecular masses of X, Y and Z are same. — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

The ebullioscopic constant is given by $K_b = \frac{R T_b^2 M}{1000 \Delta H_{\text{vap}}}$. According to Trouton's rule, the entropy of vaporization ($\Delta H_{\text{vap}} / T_b$) is approximately constant for many liquids. Thus, $K_b$ is directly proportional to the absolute boiling point $T_b$. Comparing the boiling points in Kelvin: $T_Y (300 \text{ K}) < T_X (373 \text{ K}) < T_W (455 \text{ K}) < T_Z (526 \text{ K})$. Ordering the corresponding $K_b$ values from smallest to largest gives: $0.53 (\text{Q}) < 0.68 (\text{P}) < 0.79 (\text{S}) < 0.98 (\text{R})$. Thus, Y maps to Q, X to P, W to S, and Z to R. Therefore, correct answer is A-P, B-Q, C-R, D-S.