1) Indicate the conjugate acid-base pairs in the following reactions.
a) CN- + H2O ↔ HCN + OH-
b) NH4 + H2O ↔ NH3 + H3O+
In an acid-base neutralization, an acid and a base react to form water and salt. In order for the reaction to carry out, there must be the transfer of protons between acids and bases. Proton acceptors and proton donors are the basis for these reactions, and are also referred to as conjugate bases and acids.
a) HCN (donates a proton to H2O) is acid and H3O+ (differs from H2O by one proton) is Conjugate Acid, H2O (accepts a proton from HCN) is Base CN- (differs from HCN by one proton) is Conjugate Base.
b) NH4+ is the conjugate acid to the base NH3, because NH3 gained a hydrogen ion to form NH4+, the conjugate acid. The conjugate base of an acid is formed when the acid donates a proton. In the equation, we say that OH- is the conjugate base to the acid H2O, because H2O donates a hydrogen ion to form OH-, the conjugate base.