Question

when few drops of phenolphthalein are added to dilute solution of sodium hydroxide a pink colour is produce . what will be the colour of final mixture when excess of Hcl is added to it

Answer 1

This process is done in titration.NaOH(sodium hydroxide) is a base, phenolphthalein is added and the base turns pink in colour.After titrating out the base by any acid ( drop by drop from the burette) the base gets colourless again.Titration should be in very cautious way, a single drop difference could spoil your whole experiment

Answer 2

Phenolphthalein remains colourless in neutral or acidic solution but turns out magenta or pink in basic solutions.

When it is added to NaOH, the solution has the colour of pink since sodium hydroxide is a strong base.

If HCl is added the solution loses its colour and turns out colourless since HCl neutralizes sodium hydroxide being an acid.