why phenolpthalin gives pink colour when we titrate aganist
sodium hydroxcide & phenolpthalin gives colourless titrate
aganist hydrochlric acid which is un burate



why phenolpthalin gives pink colour when we titrate aganist sodium hydroxcide & phenolpthalin ..

Answer / b.gangatharan

According to Quinonoid theory acid base indicators exist in two tautomeric forms having different structures. phenolphthalein has benzenoid form in acidic medium and thus it is colourless while it has quinonoid form in alkaline medium which has pink colour.

Thanks,
B.Gangatharan.
Caplin Point.

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