Question

Which of the following is not the characteristic of sulphanilic acid . (A) High melting point (B) Soluble in aqueous HCI (C ) Insoluble in `H_(2)O` and organic solvents (D) Insoluble in aqueous `NaOH` .
A. A,D
B. B,D
C. C,D
D. B,C

Answer 1

Correct Answer - B
Sulphailic acid has a dipolar ion (or zwitter ion) structure Being ionic it has a high melting point and structure Being ionic it has a high melting point and insoluble in `H_(2)O` as well as organic solvents As long as it exists as a dipolar ion which imarts high lattice enthalpy it will be insoluble in any given medium Thus it is insoluble in aqueous `HCI` because `-SObar_(3)` is too weakly basic to accep `H^(+)` from strong acids However it is soluble in aqueous `NaOH` because the weakly acidic `NH_(3)` transfers `H^(+)` to `OHbar` and destroys the dipolar ion to yield a simple ion `p-H_(2)NC_(6)H_(5)SObar_(3)` which imparts low lattice enthalpy .