Which of the following statements is true? a. Acids and bases cannot mix together. b. Acids and bases will neutralize each other. c. Acids, but not bases, can change the pH of a solution. d. Acids donate hydroxide ions (OH-); bases donate hydrogen ions (H+).

The answer is letter b.

Explanation:

a. Acids and bases cannot mix together. This is wrong, in fact there is a reaction called neutralization in which the reactants are an acid and a base.

b. Acids and bases will neutralize each other. This is true, when acids and bases react, the products are a salt and water and the reaction is called neutralization reaction.

c. Acids, but not bases, can change the pH of a solution. It's false, both acids and bases change the pH of a solution.

d. Acids donate hydroxide ions (OH-); bases donate hydrogen ions (H+). It's wrong, acids donate H + and bases donate OH-.