Answer to Question #22543 in Physical Chemistry for Ylber

Question

1) Indicate the conjugate acid-base pairs in the following reactions.

a) CN- + H2O ↔ HCN + OH-
b) NH4 + H2O ↔ NH3 + H3O+

Answer 1

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.