\(\text{i}\,\text{=}\,\text{1+}\{(\text{x+y})\text{-1}\}\Rightarrow \{(\text{x+y})\text{-1}\}\text{=}\,\text{i}\,\text{-}\,\text{1}\)
\(\alpha \,\, = \,\,\frac{{{\text{(i}}\,\,{\text{ - }}\,\,{\text{1)}}}}{{{\text{\{ (x}}\,\, + \,\,{\text{y)}}\,\,{\text{ - }}\,\,{\text{1\} }}}}\)
$[K_f \,(H_2O)= 1.86\,K\,kg\,mol^{-1}$ ; $K_b\,(H_2O) = 0.52\,K\,kg\,mol^{-1} ]$