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Assertion: The second dissociation constant of fumaric acid is greater than maleic acid.
Reason : Higher the dissociation constant of acid, more is the acidic character.
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Reason : Higher the dissociation constant of acid, more is the acidic character.
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If both assertion and reason are true but reason is not the correct explanation of assertion.
Both fumaric and maleic acids have two ionisable $\mathrm{H}^{+}$ions i.e., protons. The maleate monoanion shows intramolecular $\mathrm{H}$-bonding, whereas fumarate monoanion shows intermolecular $\mathrm{H}$-bonding. Thus, fumarate monoanion requires more energy to give fumarate dianion. Hence, second dissociation of fumaric acid is more than that of maleic acid.
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