Now2W2= one gram mole =M2g W1=1kg=1000g ∴Kb=
M2×x×1000
1000×M2
=xKkgmol−1 One gram mole solute dissolved in 1kg solvent =1 molal solution When concentration of solution is 1 molal, elevation in boiling point (∆Tb) is equal to molal elevation constant (Kb). Therefore, Kb=xKkgmol−1