AIIMS2017ChemistryChemical Bonding and Molecular Structure
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.
Options
- AIf both assertion and reason are true and reason is the correct explanation of assertion.
- BIf both assertion and reason are true but reason is not the correct explanation of assertion.
- CIf assertion is true but reason is false.
- DIf both assertion and reason are false.
Correct answer
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
Step-by-step solution
Both fumaric and maleic acids have two ionisable H ⁺ ions i.e., protons. The maleate monoanion shows intramolecular H -bonding, whereas fumarate monoanion shows intermolecular 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.