JEE Main 2023 — Ionic Equilibrium Question with Solution

Indicator	pH range
Methyl orange	3.2 - 4.5
Phenolpthalein	8.3 - 10.5

Option B is the incorrect statement for the use of indicators in acid-base titration.

Methyl orange is a suitable indicator for a strong acid vs strong base titration, not for a weak acid vs weak base titration. In a weak acid vs weak base titration, the pH at the equivalence point is typically around 7, which is within the pH range where methyl orange undergoes a color change. Therefore, methyl orange is not suitable for use in weak acid vs weak base titrations.

The other options are correct:

Phenolphthalein is a suitable indicator for a weak acid vs strong base titration because the pH at the equivalence point is basic, which causes phenolphthalein to undergo a color change.

Methyl orange is a suitable indicator for a strong acid vs weak base titration because the pH at the equivalence point is acidic, which causes methyl orange to undergo a color change.

Phenolphthalein may be used for a strong acid vs strong base titration because the pH at the equivalence point is basic, which causes phenolphthalein to undergo a color change.