Tuesday, May 31, 2022

Why is a weak acid best titrated with a strong base?

An acid-base titration is a type of titration used to determine the concentration of an acid or base by neutralizing the acid or base with a known concentration of acid or base. Strong acid-strong base, weak acid-strong base, strong acid-weak base, and weak acid-weak base are the types of acid base titration.

In the titration of a weak acid with a strong base, protons are transferred directly from the weak acid to the hydroxide ion, in which the titrant is a strong base and the analyte is a weak acid. During titration, a titration curve indicates the strength of the corresponding acid and base as well as the pH change.

The titration curve showing the pH change throughout the titration of a strong base with a weak acid shows that initially, the pH changes extremely slowly and gradually. As the titration approaches the equivalence point, this indicates the formation of a buffer system. At the equivalence point and beyond, the curve is typical for titration of, for example, sodium hydroxide (NaOH) and hydrochloric acid (HCl). When there is an excess of NaOH, the pH change is the same as in any NaOH-dominated system. Generally phenolphthalein indicator is used for the titration of weak acids and strong bases.


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