The pink colour of the solution of NaOH to which phenolphthalene is added be-comes colourless after adding dilute HCl because HCl is an acid and phenolphthalene becomes colourless in acid medium.
The pink colour of the solution of NaOH to which phenolphthalene is added be-comes colourless after adding dilute HCl because HCl is an acid and phenolphthalene becomes colourless in acid medium.