Dueig the reaction between `HNO_(3)` and `H_(2)SO_(4)`. There is a ______ depression of freezing point.

Options

A. two-fold
B. three-fold
C. five-fold
D. four-fold

Answer

4

Explanation

`HONO_(2)+H_()SO_(4)hArr[H_(2)ONO_(2)]^(+)+HSO_(4)^(-)`
`[H_(2)ONO_(2)]^(+)hArrH_(2)O+NO_(2)`
`underline(H_(2)+H_(2)SO_(4)hArrH_(3)O^(+)+HSO_(4)^(-))`
`HNO_(2)+2H_(2)SO_(4)to overset(+)(N)O_(2)+H_(3)O^(+)+2HSO_(4)^(-)`
Since the van't Hoff factor `i=4`, there is a four fold depresion of freezing point. Salts such as nitronium perchlorate `NO_(2)^(+)ClO_^(4)^(-)` and tetrafluoroborate `NO_(2)^(+)BF_(4)^(-)` have been isolated and can be used for aromatic nitrations.