Question

When few drops of phenolphthalein are added to a dilute solution of sodium hydroxide a pink colour is produced. What will be the colour of the final mixture when excess of HCl is added to it? (justify your answer

Answer 1

its colour would be colorless because when HCL would be added in excess it will nullify the effect of base that is sodium hydroxide

Answer 2

Phenolphthalein is a weak acid, which is why when it is added in a strong base, it gives pink color and the color gets intense as the PH of the base increases.

If a strong acid such as HCL is added in this solution, it with react with base and cause neutralization. By adding HCL in the solution, the pink color of  phenolphthalein will disappear. This is also called Acid- Base Titration.