The pink colour of phenolphthalein in an alkaline medium is due to -

Phenolphthalein is a suitable indicator for the titration of:

The indicator used in the titration of $Na_2CO_3$ with $HCl$ is..................

The rapid change of $pH$ near the stoichiometric point of an acid-base titration is the basis of indicator detection. The $pH$ of the solution is related to the ratio of the concentrations of the conjugate acid $(HIn)$ and base $(In^{-})$ forms of the indicator by the expression:

Starch can be used as an indicator for the detection of traces of

$20 \ mL$ of $0.5 \ N \ HCl$ and $35 \ mL$ of $0.1 \ N \ NaOH$ are mixed. The resulting solution will