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 exists in its colorless acidic form (\(HIn\)). In basic solutions (\(pH> 10\)), it exists as its pink - colored conjugate base (\(In^{-}\)).

• Option 1: Incorrect. Phenolphthalein is colorless in acidic solution and pink in basic solution.
• Option 2: Incorrect. Phenolphthalein is added to the reaction flask (not the burette). The titrant is added from the burette.
• Option 3: Correct. As per the acid - base behavior of phenolphthalein.
• Option 4: Incorrect. Phenolphthalein is pink (not orange) in basic solution.

Answer:

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