MHT CET202617 April 2026Evening ShiftChemistryRedox ReactionsActual
Identify colour change when NaCl solution is titrated against AgNO ₃ solution using fluorescein indicator.
Options
- AColourless to pale yellow
- BReddish pink to pale yellow
- CPale yellow to reddish pink
- DColourless to reddish pink
Correct answer
C. Pale yellow to reddish pink
Step-by-step solution
The titration of NaCl against AgNO ₃ using fluorescein indicator is an example of Fajan's method (precipitation titration). Fluorescein acts as an adsorption indicator. In the aqueous solution, it exists as the fluoresceinate anion, which imparts a pale yellow (or yellowish-green) colour to the solution. During the titration, AgCl precipitates. Before the equivalence point, the AgCl particles adsorb excess Cl ^- ions, acquiring a negative charge that repels the fluoresceinate anions. Just after the equivalence poin