Chemistry · Coordination compounds · chapter 5 of 10

Class 12 Chemistry Chapter 5: Coordination Compounds Assertion-reason questions with answers

2 assertion-reason questions on Coordination Compounds, each with its answer and the reason, written from the NCERT chapter. For the CBSE board, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.

Question 1
Assertion (A): The metal–carbon bond in [Cr(CO)₆] has both σ and π character. Reason (R): Carbon of CO donates a lone pair into a vacant metal orbital, while the metal donates a filled d pair into the vacant antibonding π* orbital of CO.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.

Both are true. The lone-pair donation is the σ part of the M–C bond and the metal-to-π* donation the π part, so R explains A; the two reinforce each other (synergic bonding).

Question 2
Assertion (A): [Fe(CO)₅] has a trigonal bipyramidal structure. Reason (R): CO is a neutral ligand, so iron in [Fe(CO)₅] is in the zero oxidation state.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Both are true: [Fe(CO)₅] is trigonal bipyramidal, and with neutral CO ligands iron is Fe(0). The oxidation state does not decide the shape, so R does not explain A.

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