why does phenolphthalein turn pink in basic solution and colourless in acidic solution.?

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Solution

$P h e n o l p h t h a l e i n c a n b e r e p r e s e n t e d a s H P h . I t s a w e a k a c i d . I t g e t s d i s s o c i a t e d a s H P h \leftrightarrow H^{+} + P h^{-} C o l o u r l e s s P i n k I f y o u a d d b a s e (O H^{-} i o n), t h e H^{+} a n d O H^{-} r e a c t s t o p r o d u c e w a t e r . T h u s m o r e a n d m o r e a m o u n t o f H^{+} i s r e m o v e d f r o m t h e e q u i l i b r i u m . S o t h e r e a c t i o n p r o c e e d s t o t h e r i g h t t h u s i t s p i n k i n c o l o u r . w h e n y o u a d d a c i d t h e a m o u n t o f H^{+} i s i n c r e a s e d i n t h e r i g h t, t h u s s h i f t i n g t h e e q u i l i b r i u m t o w a r d s l e f t a n d i t s c o l o u r l e s s .$

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Similar questions

Q. Phenolphthalein is a colourless indicator that turns pink in basic solution.

Q. In acidic solution, phenolphthalein gives a pink colour. The basic solution containing phenolphthalein is colourless.

Q. Acid + Base → Turns phenolphthalein pink
More has to be added to make the resulting solution colourless.

Q. Acids turn phenolphthalein solution pink.

Question 4

Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions, respectively are
(a) red and blue.
(b) blue and red.
(c) pink and colourless.
(d) colourless and pink

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