b
આપેલ \((T_f)_s = 271.9\,K\),  \(w =1.25\,g\),  \(W = 20\,g\),  \(K_f = 1.86\),

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

\(\Delta T_f\) = મોલાલીટી \(\times\) \(K_f\)

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

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

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

\( \Rightarrow \,\,M_w\,\, = \,\,105.68\)