The elevation in boiling point ($\Delta T_b$) is a colligative property proportional to the number of solute particles in the solution. The relationship is given by the equation: $\Delta T_b = i \times K_b \times m$ .

1. Analyze the Variables: Both solutions are equimolal ($m = 0.2 \text{ mol kg}^{-1}$). The solvent is the same (water), so the ebullioscopic constant ($K_b$) is constant .

• Therefore, the difference in boiling points depends entirely on the Van't Hoff factor ($i$).

2. Compare Boiling Points: The problem states the boiling point of X is greater than that of Y. This implies the elevation in boiling point for X is higher ($\Delta T_{b(X)} > \Delta T_{b(Y)}$). Consequently, the Van't Hoff factor for X must be greater than that for Y ($i_X > i_Y$).

3. Interpret Dissociation: Dissociation increases the number of particles in solution (e.g., $NaCl \rightarrow Na^+ + Cl^-$ gives $i=2$), whereas association decreases it ($i<1$) and no change yields $i=1$ . For $i_X$ to be significantly higher (causing a higher boiling point), substance X must be undergoing dissociation, producing more particles per mole compared to Y (assuming Y is a non-electrolyte or dissociates less).