The indicator phenol red changes from yellow to red between pH 6.8 and pH 8.4. If phenol red is added to a solution, and the solution turns red, then
A)the solution is basic, and the pH must be at or below 7.0.
B)the pH of the solution must be below 6.8, and the solution is basic.
C)the pH of the solution must be below 6.8, and the solution is acidic.
D)the pH of the solution must be above 8.4, and the solution is basic.
E)the pH of the solution is above 8.4, and the solution is acidic.

Question

Quizplus · Accepted Answer

Since phenol red changes from yellow to red between pH 6.8 and pH 8.4, if the solution turns red after adding phenol red, it means the pH of the solution must be above 8.4, therefore, the solution is basic. Therefore, the only appropriate option is D.

The Indicator Phenol Red Changes from Yellow to Red Between