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Acid-base Indicator

Mediumchemistry

Phenolphthalein is suitable indicator for titration of:

Select the correct option:

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About This Question

Subject
chemistry
Chapter
practical chemistry
Topic
acid-base indicator
Difficulty
Medium
Year
2025
Tags
titrationindicator selection

Solution

Correct Answer:

Weak acid vs strong base

  1. Indicator Range: Phenolphthalein is a basic indicator with a transition range of approximately .
  2. Equivalence Point: In a titration of a weak acid ( Acetic acid) with a strong base ( ), the resulting salt undergoes anionic hydrolysis.
  3. Resulting pH: This hydrolysis makes the solution slightly basic () at the equivalence point.
  4. Selection: Since the equivalence point (typically around ) falls within the color-change range of phenolphthalein, it is the ideal indicator.
  5. Contrast: For a strong acid vs weak base titration, the equivalence point is acidic (), making Methyl Orange (range ) a better choice.

This medium difficulty chemistry question is from the chapter practical chemistry, covering the topic of acid-base indicator. It appeared in the 2025 exam.

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