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The number of correct statements about phenolphthalein is

A. It can be used as an indicator for the titration of weak acid with weak base.
B. It begins to change colour at pH = 8.4.
C. It is a

Question

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The number of correct statements about phenolphthalein is

A. It can be used as an indicator for the titration of weak acid with weak base.
B. It begins to change colour at pH = 8.4.
C. It is a weak organic base.
D. It is colourless in acidic medium.

Canvas Classes · Accepted Answer

Step 1 — Evaluate each statement:

A. Used for weak acid + weak base titration: ✗ Incorrect — no indicator works well for weak acid + weak base titration (no sharp endpoint).

B. Begins to change colour at pH = 8.4:
Phenolphthalein is a weak acid indicator: ,

Colour change begins when :
 ✓ Correct

C. It is a weak organic base: ✗ Incorrect — phenolphthalein is a weak organic acid (it donates a proton).

D. It is colourless in acidic medium: ✓ Correct — in acidic medium, phenolphthalein exists

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