Question

question 10 (1 point)
which statement is true about phenolphthalein, the indicator, in the experimental setup?
phenolphthalein is pink in acidic solution and colorless in basic solution
phenolphthalein will be added to the burette to change color when reacting dropwise in the reaction flask.
phenolphthalein is colorless in acidic solution and pink in basic solution
phenolphthalein will be colorless in acidic solution and orange in basic solution.

Explanation:

Phenolphthalein is an acid - base indicator. In acidic solutions (pH < 8.2), it is colorless. In basic solutions (pH > 10), it is pink. Let's analyze each option:

• Option 1: Incorrect. Phenolphthalein is colorless in acidic solution and pink in basic solution, not the other way around.
• Option 2: Incorrect. Phenolphthalein is added to the reaction flask (not the burette) to indicate the end - point of a titration.
• Option 3: Correct. As per the properties of phenolphthalein, it is colorless in acidic (pH < 8.2) and pink in basic (pH > 10) solutions.
• Option 4: Incorrect. Phenolphthalein is not orange in basic solution; it is pink.

Answer:

Phenolphthalein is colorless in acidic solution and pink in basic solution.