Question

HCl is a stronger acid than the ammonium ion (NH4+). Which one of the following is true?

a) equilibrium constant for hydrolysis of HCl is smaller than that for NH4+
b) Cl- is a weaker base than NH3
c) solutions of HCl will always have more hydrogen ions than solutions of NH3
d) pH of 0.1molL-1 solution of HCl will be greater than the pH of a 0.1 molL-1 solution of NH3

The answer is B, but could someone please explain it to me? I though Cl- was neutral, not basic?

Answer 1

The chloride ion is a weak conjugate base of a strong acid that is hydrochloric acid.

Step-by-step explanation:

Weak conjugate bases are produced from strong acids, and strong conjugate bases are produced from weak acids. Here hydrochloric acid is a strong acid, and when dissolved into water, it completely ionizes into H+ and Cl- ions.

Ammonia is the conjugate acid of NH2-ion which is a strong base and becomes more stable by accepting a proton. Therefore, Cl- is an ionic species and also a conjugate base of a very strong acid.