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I understand that in a solution, the salt created by a neutralisation reaction can react again with water molecules, which can further affect the pH. Is it correct to say that the hydrolysis of salts is a secondary reaction after the neutralisation reaction?

Or, in the case where there is a strong base and weak acid (which are stoichiometrically balanced), it's just because the strong base fully dissociates and the weak acid only partially dissociates, so in the end there's just more H^+ than OH^−?

Answer 1

Salt hydrolysis is a reaction where a salt's ions interact with water to influence pH. A strong base and a weak acid produce a basic solution, while a strong acid and a weak base lead to an acidic solution. Salts from strong acids and bases form neutral (pH 7) solutions.

Step-by-step explanation:

When you combine an acid and a base, you undergo a neutralization reaction to form water and a salt. However, the resulting solution's pH is not always neutral.

The hydrolysis of salts is indeed a secondary reaction where the ions from a salt react with water, leading to a slightly acidic or basic solution depending on the strength of the acid and base involved in the initial neutralization.

When a strong base neutralizes a weak acid, the produced salt usually forms a basic solution due to the presence of the weak acid's conjugate base, which can undergo hydrolysis and generate hydroxide ions (OH⁻).

Conversely, when a strong acid is mixed with a weak base, the resulting solution is slightly acidic owing to the weak base's conjugate acid, which can release hydrogen ions (H+). Salts from strong acids and strong bases generally do not hydrolyze, and thus their solutions have a pH of 7, as with sodium chloride (NaCl).

Small, highly charged metal ions, however, can form acidic solutions in water. These metal ions are often the cationic part of a salt resulting from a strong acid and can act as an acid in water, releasing H+ ions.