1.

In the titration of Cl^(-)ions in solution with AgNO_(3) sodium salt of fluorescein is used as an indicator. The equivalence point is marked with the appearance of reddish pink colour. This is due to

Answer»

adsorption of `Cl^(-)`ions by AgCl precipitate particles
adsorption of `NO^(3^(-))`ions by AgCl precipitate particles
adsorption of `AG^(+)`ions by AgCl particles followed by adsorption of FLUORESCEIN anion.
reaction of fluorescein anion with `Ag^(+)` ions in the solution

Solution :After EQUIVALENCE point, the AgCl particles adsorb `Ag^(+)` ions (present in slight excess) and then fluorescein anion. The precipitate particles turn reddish pink DUE to the COMPLEX formation between Ag and fluorescein anion.


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