`MX_(2)` dissociates into `M^(2+)` and `X^(ө)` ion in an aqueous solution, with a degree of dissociation `(alpha)` of `0.5`. The ratio of the observed depression of freezing point of the aqueous solution to the value of the depression of freezing point in absence of ionic dissociation is

Answer

2

Explanation

`MX_(2)hArr M^(2+)+2X^(-)`
`m_(0)(1-alpha) " " m_(0)alpha " " 2m_(0)alpha , m=m_(0)(1+2alpha)`
`therefore m=m_(0)(1+2xx0.5)=2m_(0)` (as given)
`((-Delta T_(f))_("observed"))/((-Delta T_(f))_("undissociated"))=i=(m)/(m_(0))=2`