Answer to Question #30403 in Chemistry for Kelly

Question

A universal indicator turns red after coming in contact with a liquid. The pH of the liquid is 4. Is the substance an acid, base or neutral. Explain.

Answer 1

A universal indicator is a pH indicator composed of a solution of several compounds that exhibits several smooth color changes over a pH value range from 1-14 to indicate the acidity or alkalinity of solutions. Generally red color means acid, green means neutral and blue means alkaline. pH is a measure of the activity of hydrogen ions (H⁺) in a solution and, therefore, its acidity or alkalinity. It ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic. So, if the pH of the liquid is 4 and the universal indicator shows a red color, it is an acid.