Given below are two statements.
Statement I: In the titration between strong acid and weak base methyl orange is suitable as an indicator.
Statement II: For titration of acetic acid with NaOH phenolphthalein is not a suitable indicator. In the light of the above statements, choose the most appropriate answer from the options given below:
Statement I: In the titration between strong acid and weak base methyl orange is suitable as an indicator.
Statement II: For titration of acetic acid with NaOH phenolphthalein is not a suitable indicator. 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 false
- (B)Both Statement I and Statement II are true
- (C)Statement I is true but Statement II is false✓ Correct
- (D)Statement I is false but Statement II is true
Answer: (C)
Solution
At the equivalence point of a strong acid-weak base titration the solution holds the salt of a weak base, which hydrolyses to give a pH below ; methyl orange changes colour over roughly pH to and therefore reports this end point correctly, so Statement I is true. Titrating acetic acid with sodium hydroxide leaves sodium acetate at the equivalence point, whose hydrolysis puts the pH above , and that is exactly the region in which phenolphthalein changes colour, from about pH to . Phenolphthalein is thus a suitable indicator for acetic acid against sodium hydroxide, so Statement II is false. Statement I is true but Statement II is false.
JEE Main · 2021 · 26 Aug 2021 · Shift 1 · Single correct option