20 g of a binary electrolyte (Molecular mass =100) are dissolved in 500 g of water. The freezing point of the solution is `-0.74^(@)C` and `K_(f)=1.86` K kg `mol^(-1)`. The degree of ionisation of eletrolyte as :

Options

A. 0.5
B. 0.75
C. 1
D. 0

Answer

C

Explanation

`Delta T_(f("cal")) = K_(f) xx W_(2)/(M_(2) xx W_(1)(kg))=(1.85 xx 10)/(100 xx 0.5) = 0.37^(@)C`
`i= (Delta T_(f "obs"))/(Delta T_(f "cal"))=0.74/0.37=2 :. alpha = (i-1)/(n-1)=(2-1)/(2-1)=1`
`:. %alpha = 1 xx 100 = 100%`