How does ethanoic acid behave as a weak acid?

Ethanoic acid behaves as a weak acid because it only partially ionises in water, releasing a small amount of hydrogen ions.

Ethanoic acid, also known as acetic acid, is a weak acid. This means that it does not fully dissociate into its ions when it is dissolved in water. Instead, only a small fraction of the acid molecules ionise to produce hydrogen ions (H+) and ethanoate ions (CH3COO-). This partial ionisation is what characterises ethanoic acid as a weak acid.

The ionisation of ethanoic acid in water can be represented by the following equilibrium equation: CH3COOH(aq) ⇌ H+(aq) + CH3COO-(aq). The double arrow indicates that the reaction can proceed in both directions, meaning that the acid can ionise to form ions, but the ions can also recombine to form the acid. This is different from strong acids, which fully ionise in water and the reaction only proceeds in one direction.

The pH of a solution of ethanoic acid is higher (less acidic) than that of a solution of a strong acid with the same concentration. This is because the concentration of hydrogen ions in the solution of ethanoic acid is lower due to its partial ionisation.

Furthermore, the weak acidic nature of ethanoic acid can be demonstrated through conductivity experiments. A solution of ethanoic acid will conduct electricity, but not as well as a solution of a strong acid of the same concentration. This is because the number of ions present in the solution, which are responsible for conducting electricity, is less in the case of ethanoic acid due to its partial ionisation.

In summary, ethanoic acid behaves as a weak acid due to its partial ionisation in water, which results in a lower concentration of hydrogen ions compared to strong acids.