$\Delta T_f = T_0 - (T_f)_s = 273-271.9$,  $\Delta T_f = 1.1$

$\Delta T_f$ = મોલાલીટી $\times$ $K_f$

અથવા  $\Delta {T_f}\,\, = \,\,\frac{w}{{M_w\,\, \times \,\,\,W}}\,\, \times \,\,1000\,\, \times \,\,{K_f}$

$M_w\,\, = \,\,\frac{{w\,\, \times \,\,1000\,\, \times \,\,{K_f}}}{{\Delta {T_f}\,\, \times \,\,W}}\,\,\,$

$\therefore \,\,\,\,M_w\,\, = \,\,\frac{{1.25\,\, \times \,1000\, \times \,\,1.86}}{{1.1\,\, \times \,\,20}}$

$ \Rightarrow \,\,M_w\,\, = \,\,105.68$