Question

How is the latent heat of fusion per gram of the solvent related to molal depression constant?

How is molal depression constant related to molar enthalpy of fusion of the solvent?

Answer 1

Molal depression constant K_f for a particular solvent can be calculated from the following relationship.

`K_f = (M R  T_f^2)/(1000 xx Delta H_"fusion")`    ...(i)

Where T_f = Freezing point of solvent

`Delta H_"fusion"` = Molar enthalpy of fusion of frozen solvent (Latent heat of fusion for one mole of frozen solvent)

M = Molecular mass of solvent

R = Gas constant

The latent heat of fusion per gram of the solvent (L_f) is related to `Delta H_"fusion"` as

`L_f = (Delta H_"fusion")/M`

Therefore, equation (i) can also be written as

`K_f = (R  T_f^2)/(1000 L_f)`