It is a case of salt hydrolysis. `NaNO_(3)` [salt of strong acid `(HNO_(3))` and strong base `(NaOH)`] does not undergo hydrolysis. Thus, its aqueous solution is neutral `(pH=7)`. `NH_(4)Cl` [salt of strong acidf `(HCl)` and weak base `(NH_(3)`] undergoes cationic hydrolysis. Thus, its aqueous solution is acidic `(pHlt7)`. Both `CH_(3)COOK` and `Na_(2)CO_(3)` are salts of strong base and weak acid. They undergo anion hydrolysis to provide basic solution `(pHgt7)`. However, `CO_(3)^(2-)` ion is a relatively stronger base than `CH_(3)COO^(-)` ion a (as `H_(2)CO_(3)` is a weaker acid than `CH_(3)COO`). Hence, `Na_(2)CO_(3)` solution is most basic and has the highest pH.
