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Question: Answered & Verified by Expert
Assertion : $\mathrm{La}(\mathrm{OH})_3$ is more basic than $\mathrm{Lu}(\mathrm{OH})_3$.Reason : Size of $\mathrm{Lu}^{3+}$ increases and shows more covalent character.
ChemistryChemical Bonding and Molecular StructureAIIMSAIIMS 2012
Options:
  • A If both assertion and reason are true and reason is the correct explanation of assertion
  • B If both assertion and reason are true but reason is not the correct explanation of assertion
  • C If assertion is true but reason is false
  • D If both assertion and reason are false.
Solution:
1947 Upvotes Verified Answer
The correct answer is: If assertion is true but reason is false
Due to lanthanide contraction, the size of $\mathrm{Lu}^{3+}$ is decreased and therefore $\mathrm{Lu}(\mathrm{OH})_3$ shows more covalent character (Small cation, more is covalent character - Fajan's rule). Thus $\mathrm{La}(\mathrm{OH})_3$ is more ionic and thus more basic.

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