JEE Main 2023ChemistryD And F Block ElementsProperties Of Transition ElementsmediumMCQ

JEE Main 2023 — D And F Block Elements Question with Solution

From: JEE Main 2023 (Online) 6th April Evening Shift

Question

Given below are two statements: one is labelled as "Assertion A" and the other is labelled as "Reason R"

Assertion A : In the complex and , the metals have zero oxidation state.

Reason R : Low oxidation states are found when a complex has ligands capable of -donor character in addition to the -bonding.

In the light of the above statements, choose the most appropriate answer from the options given below

Choose an option

Show full solutionCorrect option: B
Correct answer
BA is correct but R is not correct

Step-by-step explanation

  • Option B: "A is correct but R is incorrect" is the right answer. Here is the reasoning:

    • Assertion A is correct. In the complex , if we assume the oxidation state of Ni to be x, we can set up the equation:

    $ x + (0 \times 4) = 0 $

    From which we find that (x = 0).

    Similarly, in , if we let the oxidation state of Fe be y, the equation becomes:

    $ y + (0 \times 5) = 0 $

    Solving this gives (y = 0).

    Therefore, the oxidation states of both Ni and Fe are zero in their respective complexes, verifying that Assertion A is true.

    Regarding Reason R, it is incorrect. The low oxidation states in these complexes are stabilized through synergic bonding, which involves the ligand being a -acceptor, not a -donor. The CO ligand in these complexes accepts electron density from the metal into its antibonding molecular orbitals, characterizing a -acid ligand, and not a -donor ligand as stated. Consequently, Reason R does not hold true.

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    About this question

    This is a previous-year question from JEE Main 2023, covering the D And F Block Elements chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.