Question

Q. Define- i) Molal elevation constant. ii) Molal Depression constant.

Answer 1

molal elevation constant -
it is the elevation in boiling point for one molal solution.it is also know as the ebullioscopic constant.

molal depression constant -
it is the depression in freezing point for one molal solution.it is also know as the cryoacopic constant

Answer 2

Answer: Molal elevation constant is defined as the elevation in boiling point when the molality of the solution is unity, i.e 1 mole of the solute is dissolved in 1 kg of the solvent. The units of molal elevation constant represented by $K_b$ is $Kkgmol^{-1}$

$\Delta T_b=K_b\times m$

$\Delta T_b$ = change in boiling point

$k_f$ = Molal elevation constant

m = molality

Molal depression constant is defined as the depression in freezing point when the molality of the solution is unity, i.e 1 mole of the solute is dissolved in 1 kg of the solvent. The units of molal freezing constant represented by $K_f$ is $Kkgmol^{-1}$

$\Delta T_f=k_f\times m$

$\Delta T_f$ = change in freezing point

$k_f$ =Molal depression constant

m = molality