Which of the following solvents is having its lowest Ebullioscopic co…

The correct answer is Option (2) → Diethyl Ether

The ebullioscopic (molal elevation) constant K_b is the elevation of boiling point for a 1 molal solution. It depends on the solvent:

    \( \displaystyle K_b=\frac{R\,M_1\,T_b^{2}}{1000\,\Delta_{vap}H} \)

where M₁ is the molar mass of the solvent and T_b its boiling point. So the boiling point alone does not fix K_b; the molar mass and the enthalpy of vaporisation also count.

Table 1.3 gives the lowest K_b of the four, 2.02 K kg mol⁻¹, for diethyl ether.

NCERT (2026-27 edition):
Elevation of Boiling Point – …