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Question: Answered & Verified by Expert
Most basic hydroxide among the following is
Chemistryd and f Block ElementsMHT CETMHT CET 2009
Options:
  • A $\mathrm{Lu}(\mathrm{OH})_{3}$
  • B $\mathrm{Eu}(\mathrm{OH})_{3}$
  • C $\mathrm{Yb}(\mathrm{OH})_{3}$
  • D $\mathrm{Ce}(\mathrm{OH})_{3}$
Solution:
1324 Upvotes Verified Answer
The correct answer is: $\mathrm{Ce}(\mathrm{OH})_{3}$
Due to lanthanide contraction, the size of $M^{3+}$ ions [ie, $\mathrm{Lu}^{3+}, \mathrm{Eu}^{3+}, \mathrm{Yb}^{3+}$ and $\mathrm{Ce}^{3+}$ ] decreases
and thus, the basic strength of their hydroxides decreases.
The order of size of given $M^{3+}$ ions is $\mathrm{Ce}^{3+}>\mathrm{Eu}^{3+}>\mathrm{Yb}^{3+}>\mathrm{Lu}^{3+}$
$\therefore$ The order of basic strength of hydroxides is $\mathrm{Ce}(\mathrm{OH})_{3}>\mathrm{Eu}(\mathrm{OH})_{3}>\mathrm{Yb}(\mathrm{OH})_{3}>\mathrm{Lu}(\mathrm{OH})_{3}$
(most basic)

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