Answer
(a) Base. $Ca(OH)_2(aq) --\gt Ca^{2+}(aq) + 2OH^-(aq)$
(b) Acid. $HC_2H_3O_2(aq) + H_2O(l) \lt -- \gt C_2H_3O_2^-(aq) + H_3O^+(aq)$
(c) Base: $KOH(aq) -- \gt K^+(aq) + OH^-(aq)$
(d) Acid: $HNO_3(aq) + H_2O(l) -- \gt NO_3^-(aq) + H_3O^+(aq)$
Work Step by Step
(a) and (c): The "OH" in the molecule indicates that it can act as a base.
(b) and (d): The isolated "H" as the first letter of the formula indicates that it can act as an acid.
- According to the Arrhenius definition:
Acid: Produces $H^+$ in aqueous solution;
Base: Produces $OH^-$ in aqueous solution;