To complete the sentence, we need to understand the reaction between an acid and water. When an acid is added to water, it donates hydrogen ions (H+) to the water. Therefore, the correct answer is that hydrogen ions increase.
soap is made from either sodum hydroxide, or potassium hydroxid, and fat. Hydroxides are very basic.
when an acid is added to water, hydronium ions are put in solution in excess of hydroxide ions.
