The titration curve of a weak acid vs. a stro | vedclass

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(B) $pK_{In} = -\log(4 	imes 10^{-10}) = -(\log 4 + \log 10^{-10}) = -(0.6 - 10) = 9.4$.The indicator range is given by $pK_{In} \pm 1$,which is $8.4

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$2$

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(B) $pK_{In} = -\log(4 	imes 10^{-10}) = -(\log 4 + \log 10^{-10}) = -(0.6 - 10) = 9.4$.The indicator range is given by $pK_{In} \pm 1$,which is $8.4$ to $10.4$.Statement $A$: Incorrect. Phenolphthalein is not suitable for weak acid-weak base titrations because the pH change is not sharp enough.Statement $B$: Correct. The colour change range starts at $pH = pK_{In} - 1 = 9.4 - 1 = 8.4$.Statement $C$: Incorrect. Phenolphthalein is a weak organic acid $(HIn)$.Statement $D$: Correct. In an acidic medium,the equilibrium $HIn ightleftharpoons H^+ + In^-$ shifts to the left,keeping it in the unionized $HIn$ form,which is colourless.Therefore,statements $B$ and $D$ are correct. The total number of correct statements is $2$.

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