Why should the endpoint be taken as the faint pink color of the indicator?

Answer 1

When using an indicator in a titration, the color changes happen when the titrant has reacted with all the substance of interest in the sample. As soon as the titrant isn't reacting with the sample any more, it starts reacting with the indicator, and continuing past the first hint of color will be using too much titrant, and the calculations for the concentration of the sample will be wrong.

Phenolphthalein starts out pink, but will turn red as the pH keeps changing as you go further past the endpoint of the titration.

Answer 2

The faint pink color indicates that the solution is nearing the endpoint of the titration, where the reaction is nearly complete. Taking the faint pink color as the endpoint ensures accurate results without risking over-titrating the solution, which could lead to inaccurate readings.

Answer 3

Because faint pink color of the phenolphthalein indicator indicate the endpoint, in an acid base titration

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