Of the following, the amphiprotic ion is (a) \(\mathrm{HCO}_{3}^{-}\) (b) \(\mathrm{CO}_{3}^{2-} ;\) (c) \(\mathrm{NH}_{4}^{+} ;\) (d) \(\mathrm{CH}_{3} \mathrm{NH}_{3}^{+} ;\) (e) \(\mathrm{ClO}_{4}^{-}\).

An amphiprotic ion can act as both an acid and a base. This means it can donate a proton (H+) to become a conjugate base or accept a proton (H+) to become a conjugate acid, depending on the environment.

(a) \(\mathrm{HCO}_{3}^{-}\): This ion can lose a H+ ion to become \(\mathrm{CO}_{3}^{2-}\) or gain a H+ ion to become \(\mathrm{H}_{2}\mathrm{CO}_{3}\). Therefore, it is amphiprotic. \n(b) \(\mathrm{CO}_{3}^{2-}\): This ion can only accept a H+ to become \(\mathrm{HCO}_{3}^{-}\). Therefore, it is not amphiprotic. \n(c) \(\mathrm{NH}_{4}^{+}\): This ion can only lose a H+ ion to become \(\mathrm{NH}_{3}\). Therefore, it is not amphiprotic. \n(d) \(\mathrm{CH}_{3}\mathrm{NH}_{3}^{+}\): This ion can only lose a H+ ion to become \(\mathrm{CH}_{3}\mathrm{NH}_{2}\). Therefore, it is not amphiprotic. \n(e) \(\mathrm{ClO}_{4}^{-}\): This ion is a stable anion and cannot lose or accept a proton. Therefore, it is not amphiprotic.

Only one ion shows the capability of both accepting and donating a proton, which makes it amphiprotic. That ion is \(\mathrm{HCO}_{3}^{-}\).