Question

Assertion : $La(OH{)}_3$ is more basic than $Lu(OH{)}_3$.
Reason : Size of $L{u}^{3+}$ increases and shows more covalent character.

• 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

Answer 1

Answer: (C)

Due to lanthanide contraction, the size of Lu³⁺ is decreased and therefore Lu(OH)₃ shows more covalent character (Small cation, more is covalent character - Fajan’s rule). Thus La(OH)₃ is more ionic and thus more basic.