At `100 ^(@) C` the vapour pressure of a solution containing 6.5 g a solute in 100 g water is 732mm.If ` K_b =0.52`, the boiling point of this solution will be

Options

A. ` 102 ^(@)C`
B. `100^(@)C`
C. `101^(@)C`
D. `100.52 ^(@)C`

Answer

C

Explanation

`(Delta P )/( P ^(@)) = (n _(2))/( n _(1))`
`W _(2) = 65g`
`W_(1) = 100g`
` K _(b ) =0.52`
`(Delta P )/( P ^(@)) = (W_(2) M _(1))/( M _(2) W _(1))`
`(760 - 732)/(760)= (6.5 xx 18)/(m _(2) xx 100)`
`M _(2) = 31.75 `
`Delta T _(b ) = K _(b) . m = (0.52 xx 6.5 xx 1000)/( 31. 75 xx 100) = 1. 06`
`T _(b) - 100 =1. 06`
`T _(b) = 100 + 1.06 = 101. 06 ~~ 101^(@)C`