Question

Molal depression constant $k_{f}$ is always greater than molal elevation constant $k_{b}$ for any solvent. It is because

• A. the magnitude of Enthalpy of vapourisation is greater than the magnitude of Enthalpy of Fusion.
• B. $k_{f}$ and $k_{b}$ are inversely proportional to Enthalpy of vapourisation and Enthalpy of fusion respectively.
• C. $k_{f}$ and $k_{b}$ are inversely proportional to Enthalpy of fusion and Enthalpy of vapourisation respectively.
• D. of both (1) and (3) statements.

Answer 1

Answer: (D)

$k_{f}=\frac{R T_{f}^{2} M}{1000 \Delta H_{\text {filsion }}}$ and $k_{b}=\frac{R T_{b}^{2} M}{1000 \Delta H_{\text {vapourisation }}}$ and
$\Delta H_{\text {vapourisation }}>\Delta H_{\text {filsion }}$