Classify the following substances as acidic, basic, or neutral: a. a soapy solution, pH = 9 b. a sour liquid, pH = 5 c. a solution with four times as many hydronium ions as hydroxide ions

A. Soapy solution (pH of 9) = basic

B. Sour liquid (pH of 5) = acidic

C. Solution with four times as many hydronium (H+) ions as hydroxide ions (OH-) = acidic

Soapy solution with a pH of 9 is basic because it has a pH greater than 7. The same goes for the sour liquid with a pH of 5, which has a pH lower than 7, making it acidic. The word sour also hints at it being acidic because of the definition of Bronsted acids. Finally, higher H + ion concentrations make a solution more acidic.