Acidity of Carboxylic Acids

Acids produce hydrogen ions (H+) in aqueous solutions.

The strength of an acid can therefore be determined by the amount of hydrogen ions it produces in an aqueous solution.


Strong Acids

A strong acid is completely ionised in aqueous solution. Examples of strong acids include hydrochloric, nitric and sulfuric acids.

The aqueous solutions of strong acids have a high concentration of hydrogen ions (H+). This gives them a low number on the pH scale.



Weak Acids

Weak acids only undergo partial ionisation in aqueous solutions. Carboxylic acids are examples of weak acids.

Only some of the carboxylic acid molecules ionise in aqueous solution to form H+ ions. This results in the aqueous solution of weak acids having a higher number on the pH scale.

A weak acid such as a carboxylic acid has a lower degree of ionisation in an aqueous solution than a strong acid. Thus, for a given concentration of an aqueous solution, the stronger the acid, the lower the pH.

The pH scale is used for measuring the acidity or alkalinity of a solution. It is a logarithmic scale and as the pH decreases by one unit the hydrogen ion concentration of the solution increases by a factor of 10. A solution of pH 7 is neutral. So weak acids such as carboxylic acids have a pH below 7.