Given below are two statements: one is labell | vedclass

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(D) Phenolphthalein $(HPh)$ is a weak organic acid.In an acidic medium,the equilibrium $HPh \rightleftharpoons H^{+} + Ph^{-}$ shifts to the left due

Vedclass · Accepted Answer

$A$ is true but $R$ is false.

Vedclass · Answer

(D) Phenolphthalein $(HPh)$ is a weak organic acid.In an acidic medium,the equilibrium $HPh \rightleftharpoons H^{+} + Ph^{-}$ shifts to the left due to the common ion effect of $H^{+}$ ions,keeping the concentration of the unionized form $(HPh)$ high,which is colourless.In a basic medium,the $OH^{-}$ ions react with $H^{+}$ to form water,shifting the equilibrium to the right. This increases the concentration of the ionized form $(Ph^{-})$,which is pink in colour.Therefore,Assertion $A$ is true,but Reason $R$ is false because phenolphthalein does dissociate in a basic medium.

Similar Questions

For which of the following titrations is phenolphthalein the most suitable indicator?

Which indicator is used for the titration of $CH_3COOH$ and $NaOH$?

If a very small amount of $HPh$ (phenolphthalein) is added to a $0.1 \ M$ aqueous solution of $CH_3COONa$,the fraction of the indicator that exists in the colourless form is:
$[K_b(CH_3COO^{-}) = 10^{-9}, pK_a(HPh) = 9.6, \log 2 = 0.3]$

In an acid-base titration,the rapid change in $pH$ near the equivalence point depends on the indicator used. 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 which equation?

Phenolphthalein is not suitable for the titration of

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