Question

Phenolphthalein does not act as an indicator for
the titration between :-
(1) KOH and H2SO4
(2) NaOH and CH3COOH
(3) Oxalic acid and KMnO4
(4) Ba(OH)2 and HCI​

Answer 1

Explanation:

because phenolpthalein changes its colour between pH 8.1-10, and for titration of strong acid and weak base pH is slightly less than 7, so it does not show any change in colour, hence it is not suitable indicator for strong acid – weak base titration. A strong acid- strong base titration is performed using a phenolphthalein indicator. Phenolphtalein is chosen because it changes color in a pH range between 8.3 – 10. It will appear pink in basic solutions and clear in acidic solutions.