An aqueous solution of `(NH_(4))_(2)SO_(4)` is acidic. Explain.

Explanation

`(NH_(4))_(2)SO_(4)` is salt of weak base `(NH_(3))` and a strong acid `(H_(2)SO_(4))`. In its aqueous solution, `(NH_(4))_(2)SO_(4)` dissociates almost completely forming `NH_(4)^(+) and SO_(4)^(2-)` ions. `SO_(4)^(2-)` ion is a conjugate base of strong acid `H_(2)SO_(4)` and hence in aqueous solution it is a very weak base in comparison to `H_(2)O`. as a result, `SO_(4)^(2-)` ion does not react with water in aqueous solution. on the other hand, `NH_(4)^(+)` is a conjugate acid of weak base `NH_(3)`. in aqueous solution, `NH_(4)^(+)` ion shows higher acidic character than `H_(2)O`. as a result, `NH_(4)^(+)` ions react with water `[NH_(4)^(+)(aq)+H_(2)O(l)hArr NH_(3)(aq)+H_(3)O^(+)(aq)]`, causing an increase n concentration of `H_(3)O^(+)(aq)` ions in the solution. this makes the solution of `(NH_(4))_(2)SO_(4)` acidic.