Q50 / 180 · AIIMS 2005 · Chemistry

Assertion : $\mathrm{SiF}_6{ }^{2-}$ is known but $\mathrm{SiCl}_6{ }^{2-}$ is not. Reason : Size of fluorine is small and its lone pair of electrons interacts with $d$-orbitals of $\mathrm{Si}$ strongly.

  • Correct answer
    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

(i) Due to smaller size of $F$, steric repulsions will be less in $\mathrm{SiF}_6{ }^{2-}$. (ii) Interaction of $\mathrm{F}$ lone pair electrons with $\mathrm{Si}$ is stronger than that of chlorine lone pairs.

Hence, the correct answer is option: 'A'.

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