Search any question & find its solution
Question:
Answered & Verified by Expert
Assertion (A) : pKa of phenol is 4.19 and that of benzoic acid is 10
Reason (R) : Phenoxide ion is stabilised by nonequivalent resonance structures whereas benzoate ion by two equivalent resonance structures
The correct option among the following is
Options:
Reason (R) : Phenoxide ion is stabilised by nonequivalent resonance structures whereas benzoate ion by two equivalent resonance structures
The correct option among the following is
Solution:
2520 Upvotes
Verified Answer
The correct answer is:
A is false but R is true
$\mathrm{pK}_{\mathrm{a}}=-\log \mathrm{K}_{\mathrm{a}}$ so as $\mathrm{K}_{\mathrm{a}}$ increases, $\mathrm{pK}_{\mathrm{a}}$ decreases. Benzoic acid is a stronger acid than phenol so its $\mathrm{pK}_{\mathrm{a}}$ will be smaller than that of phenol.
Thus, Assertion (A) is false.
The resonance structures of phenoxide ion and benzoate ion are given by:-
Thus, Reason (R) is true.
Thus, Assertion (A) is false.
The resonance structures of phenoxide ion and benzoate ion are given by:-
Thus, Reason (R) is true.
Looking for more such questions to practice?
Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.