Question

An indicator (Phenolphthalein) gives pink color in a basic solution and gives no color in an acidic solution.

a) What color is observed in a solution of pH = 5
b) What color is observed in a solution of pH = 14
c) What color is observed in a solution of pH < 7
d) What color is observed in a solution of pH = 0

Answer 1

At a pH of 5, the solution with phenolphthalein will be colorless. At a pH of 14, it will be pink, as it will with any pH greater than 8.3, and it will remain colorless for any pH less than 7, including at pH 0.

Step-by-step explanation:

Phenolphthalein is an acid-base indicator commonly used in titrations to determine the pH level of a solution. As such:

• a) At a pH of 5, the solution will be colorless, indicating an acidic environment.
• b) At a pH of 14, the solution will be pink, indicating a basic (alkaline) environment.
• c) At a pH less than 7, regardless of the exact value, the solution will be colorless as it is in the acidic pH range.
• d) At a pH of 0, which is highly acidic, the solution will be colorless.

Phenolphthalein changes from colorless to pink as the environment shifts from acidic (pH < 8.3) to basic (pH > 8.3), with the pink color indicative of a basic solution due to a lower hydronium ion concentration.