Final answer:
A salt is more soluble in an acidic solution if it contains the conjugate base of a weak acid, as the excess H+ in the acid reacts with the anion to form its conjugate acid, reducing the concentration of the anion in solution and driving the dissolution process according to Le Chatelier's principle.
Step-by-step explanation:
To determine if a salt is more soluble in acid than in water, one must consider the acid-base properties of the salt's ions. A salt comprised of the conjugate base of a weak acid will generally become more soluble in an acidic solution due to the common ion effect, as described by Le Chatelier's principle. This is because, in the presence of excess H+, the equilibrium shifts to produce more solute from the precipitate to decrease the concentration of the conjugate base in solution.
Evaluating the solubility of a salt also involves conducting experiments, such as dissolving the salt in water compared to an acidic solution and observing any notable differences in the amount of salt that dissolves. For example, a sparingly soluble salt like Mg(OH)2 will show increased solubility in an acidic solution like HCl, since the added H+ ions will react with the OH- ions to form water, driving the dissolution process forward.
In summary, the solubility of a salt in an acidic environment is influenced by the propensity of the anion to react with H+ to form the conjugate acid. This process, known as hydrolysis, is favoured for anions that are the conjugate bases of weak acids and is a key factor in increasing the solubility of certain salts in acidic solutions.