Incorrect statement for the use of indicators in acid-base titration is :
- (A)Methyl orange may be used for a weak acid vs weak base titration.✓ Correct
- (B)Methyl orange is a suitable indicator for a strong acid vs weak base titration
- (C)Phenolphthalein is a suitable indicator for a weak acid vs strong base titration
- (D)Phenolphthalein may be used for a strong acid vs strong base titration.
Answer: (A)
Solution
Methyl orange, changing colour over about pH 3.1 to 4.4, is suited to strong acid against weak base and to strong acid against strong base; phenolphthalein, changing over about pH 8.3 to 10, is suited to weak acid against strong base and to strong acid against strong base. A weak acid versus weak base titration has no sharp break in pH at the equivalence point, so no ordinary indicator, methyl orange included, can mark its end point. The statement that is not correct is the one claiming methyl orange may be used for a weak acid versus weak base titration.
JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Single correct option