Which chemical is known to convert carboxyl ions in surfactants to carboxyl acid?

The chemical that is known to convert carboxyl ions in surfactants to carboxyl acid is sulfuric acid. This transformation occurs because sulfuric acid is a strong acid that can donate protons (H⁺) to carboxylate ions, thereby converting them back into their corresponding carboxylic acids.

In the context of surfactants, which are often derived from fatty acids, the presence of the -COO⁻ (carboxylate ion) form indicates a deprotonated state where the hydrogen from the carboxyl group is removed, usually due to basic conditions. Introducing a strong acid like sulfuric acid can effectively protonate the carboxylate ions, returning them to the acid form. This reaction is particularly relevant in applications such as formulation adjustments in detergent chemistry, where the pH must be manipulated to achieve desired properties.

Other options, such as sodium hydroxide and calcium hydroxide, are basic compounds and would increase the pH further, which would not convert carboxylate ions back to carboxylic acids. Trisodium phosphate is also a basic compound that would similarly not facilitate this conversion. Thus, sulfuric acid stands out as the correct choice for its ability to