Question

Match the Indicators (List-I) with their pH range (List-II): A. Methyl orange, B. Phenolphthalein, C. Methyl red, D. Phenol red. Ranges: I. 6.8-8.4, II. 4.2-6.3, III. 3.1-4.4, IV. 8.3-10.0.

• A. A-III, B-II, C-I, D-IV
• B. A-II, B-IV, C-III, D-I
• C. A-III, B-IV, C-II, D-I
• D. A-III, B-I, C-II, D-IV

Hint:

"Orange" is the most acidic (3-4), "Red" is middle (4-6), "Phenolphthalein" is for base (8-10).

Answer 1

The Correct Option is C

Step 1: Concept Indicators are weak acids or bases that change color within specific pH intervals depending on their $pK_{a}$.

Step 2: Meaning Acidic indicators have lower ranges (Methyl group), while basic indicators like Phenolphthalein have higher ranges.

Step 3: Analysis Methyl orange (A) is highly acidic, range 3.1-4.4 (III). Methyl red (C) is slightly less acidic, range 4.2-6.3 (II). Phenol red (D) works near neutrality, range 6.8-8.4 (I). Phenolphthalein (B) is for basic titrations, range 8.3-10.0 (IV).

Step 4: Conclusion The matching follows A-III, B-IV, C-II, D-I. Final Answer: (C)