Why does the addition of acid increase the solubility of calcium phosphate? a. It decreases the phosphate ion concentration, forcing the equilibrium to the right. b. It increases the phosphate ion concentration, forcing equilibrium to the left. c. It decreases the phosphate ion concentration, forcing the equilibrium to the left. d. It increases the phosphate ion concentration, forcing the equilibrium to the right. e. It decreases the calcium ion concentration, forcing the equilibrium to the right. f. It increases the calcium ion concentration, forcing the equilibrium to the right. g. It decreases the calcium ion concentration, forcing the equilibrium to the left. h. It increases the calcium ion concentration, forcing equilibrium to the left.

Answer: c. It decreases the phosphate ion concentration, forcing the equilibrium to the left.

Explanation:

The calcium phosphate in water is dissociated according to the following equilibrium:

Ca₃ (PO₄) ₂ ⇄ 3Ca²⁺ + 2PO₄³⁻

A neutralization reaction is one in which an acid reacts with a base. In the reaction a salt is formed and in most cases water is formed.

Phosphate is the complementary base of phosphoric acid, so when adding acid to the solution, we will neutralize the phosphate present according to the following reaction:

PO₄³⁻ + 3H⁺ ⇄ H₃PO₄

Therefore, when adding acid we increase the solubility of calcium phosphate since we are neutralizing the phosphate present in the salt, decreasing the concentration of phosphate, displacing the first equilibrium shown to the left and favoring the dissolution of calcium phosphate.