Elevation in boiling point for 1 . 5 molal solution of glucose in...

Elevation in boiling point $∆ {T}_{b} = {ik}_{b}{m}_{1}$

Depression in freezing point $∆ {T}_{f} = {ik}_{f}{m}_{2}$

$4 = {ik}_{b}\left(1 . 5\right)$

$4 = {ik}_{f}\left(4 . 5\right)$

Dividing both:

$\dfrac{{k}_{b}}{{k}_{f}} = \dfrac{3}{1}$

Hence, The ratio of molal elevation constant to molal depression constant is 3:1