Question

Consider a monoprotic weak acid (HA) that is titrated with a strong base. What is the relationship between the strength of the weak acid and the pH of the solution at the equivalence point? 

There is no relationship between the strength of the acid and the pH at the equivalence point.

The pH at the equivalence point is always 7 in an acid base titration.

The weaker the acid, the higher the pH at the equivalence point.

The stronger the acid, the higher the pH at the equivalence point. 

Answer 1

When a weak acid and strong base reacts, a salt is formed at equivalence point. This salt will be basic as it is a combination of weak acid and strong base.

The higher the basic character of a compound, the higher will be its \(\mathrm{pH}\). The \(\mathrm{pH}\) of base is generally above 7 . The higher the acidic character of a compound, the lower will be its \(\mathrm{pH}\). The \(\mathrm{pH}\) of acid is generally below 7 .

Therefore, the \(\mathrm{pH}\) of any compound is inversely proportional to its acidic character. So, the weak will be acid the higher will be its \(\mathrm{pH}\) at equivalence point.