$ = \,\,\frac{X}{{X\,\, + \,\,\frac{{1000}}{{78}}}}\,\, = \,\,\frac{X}{{X\,\, + \,\,12.82}}$
$ \Rightarrow \,\,0.2\,\, = \,\,\,\frac{X}{{X\,\, + \,\,12.82}}$ $ \Rightarrow \,\,X\,\, = \,\,3.2$
(પાણી માટે $K_f = 1.86\,^oC\, kg\, mol^{-1}$ છે)
(મોલર દળ $S = 32\, g\, mol^{-1}, Na = 23\, g\, mol^{-1}$ )