The amino acid, alanine, dissolves in water - VCE - SSCE Chemistry - Question 9 - 2002 - Paper 1

To determine how alanine behaves in an aqueous solution at pH 7, we must consider its structure and the nature of amino acids. Alanine, being an amino acid, contains both a carboxyl group (-COOH) and an amino group (-NH2).

At a neutral pH of 7, the carboxyl group tends to lose a proton, acting as an acid, while the amino group tends to gain a proton, acting as a base. Hence, alanine is capable of acting both as an acid and a base. This property is known as amphoteric character, which is typical for amino acids.

Therefore, the correct answer is: D. both an acid and a base.