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NEETChemistryd and f Block Elements

Consider the following statements regarding the chromate and dichromate ions: (I) The yellow colour of chromate ion changes to orange dichromate ion in acidic medium. (II) During the conversion of chromate to dichromate, the oxidation state of chromium changes from +6 to +7 . (III) The chromate ion has a tetrahedral geometry. (IV) The dichromate ion consists of two tetrahedra sharing one oxygen corner with a Cr - O -

Options

  1. A3
  2. B4
  3. C2
  4. D1

Correct answer

A. 3

Step-by-step solution

Statement (I) is correct: Chromate ( CrO ₄²⁻ ) is yellow and changes to orange dichromate ( Cr ₂ O ₇²⁻ ) in acidic medium. Statement (II) is incorrect: The oxidation state of chromium in both chromate and dichromate ions is +6 . The interconversion is a pH-dependent equilibrium, not a redox reaction. Statement (III) is correct: The chromate ion has a tetrahedral geometry. Statement (IV) is correct: The dichromate ion consists of two tetrahedra sharing one oxygen corner with a Cr - O - Cr bond angle of 126^ . Theref

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