What is the freezing point of a solution containing `8.1g Br `in `100g` water assuming the acid to be `90%`ionised(`K_(f)`for water =`1.8K "mole"^(-1))`

Options

A. `0.85^(@)C`
B. `-3.53^(@)C`
C. `0^(@)C`
D. `-0.35^(@)C`

Answer

B

Explanation

`{:(HBr,hArr,H^(+),+,Br^(-)),((1-alpha),,alpha,,alpha):}`
Total `= 1+alpha therefore i=1+alpha=1+0.9=1.9`
`Delta T_(f)= i K_(f)xx m=1.9xx1.86xx(8.1)/(81)xx(1000)/(100)=3.53^(@)C`
`T_(f)=-3.53^(@)C`.