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JEE Advanced levelSingle correct optionDifficulty 3 of 3cb050

Assertion (A): All three C-O bonds in have the same length. Reason (R): The carbonate ion rapidly flips among three structures, each with different C-O bond lengths.

  1. ABoth A and R are true and R is the correct explanation of A
  2. BBoth A and R are true but R is not the correct explanation of A
  3. CA is true but R is false
  4. DA is false but R is true

Answer: C

A is true: delocalisation makes the three bonds equal (bond order 4/3). R is false: the canonical structures are only contributors to one real hybrid; the ion does not interconvert among them.
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