JEE Main 2023 · 8 April · evening · Single correct · +4 / −1
Given below are two statements:
Statement I : In redox titration, the indicators used are sensitive to change in pH of the solution.
Statement II : In acid-base titration, the indicators used are sensitive to change in oxidation potential.
In the light of the above statements, choose the most appropriate answer from the options given below
- (a) Both Statement I and Statement II are incorrect
- (b) Statement I is correct but Statement II is incorrect
- (c) Statement I is incorrect but Statement II is correct
- (d) Both Statement I and Statement II are correct
Answer and solution
Answer (a) Both Statement I and Statement II are incorrect
Solution
Chemistry ma’am · 3 steps
The two statements have swapped their indicators: put each one back with its own titration.
- Redox titration. Here electrons move, so the oxidation potential of the solution changes sharply at the end point. Redox indicators such as diphenylamine are themselves oxidised or reduced, and they change colour in response to that potential, not to pH.
- Acid-base titration. Here H⁺ is neutralised by OH⁻, so the pH jumps at the end point. Indicators such as phenolphthalein and methyl orange are weak acids or bases whose colour depends on pH, not on oxidation potential.
Titration What changes sharply Indicator responds to Statement says Redox oxidation potential oxidation potential pH, so I is incorrect Acid-base pH pH oxidation potential, so II is incorrect - So. Both statements pair the indicator with the wrong property, so both are incorrect. The answer is (a).
The idea to keep. An indicator must respond to whatever jumps at the end point. In redox titrations that is the oxidation potential, and in acid-base titrations it is the pH.
Answer from the NTA final answer key. Solution by PrepWiser.