Phenolphthalein is an acid-base indicator that is colorless in its acid form and pink in its basic form, changing at pH = 8.5. Bromcresol green is yellow in its acidic form and blue in its basic form, changing at pH = 4.8. A solution is colorless in phenolphthalein and blue in bromcresol green. Therefore we can conclude that the pH of the solution is ____.
A) exactly 7.0
B) greater than 8.5
C) between 7.0 and 8.5
D) between 4.8 and 8.5
E) less than 4.8

Question

Quizplus · Accepted Answer

Since the solution is colorless in phenolphthalein, it must have a pH lower than 8.5. Since the solution is blue in bromcresol green, it must have a pH higher than 4.8. Therefore, the pH of the solution is between 4.8 and 8.5, making choice D the correct answer.

Phenolphthalein Is an Acid-Base Indicator That Is Colorless in Its