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Order complexes by the energy or wavelength of light absorbed (spectrochemical series)

This type of question, asked 9 times: 2021 Paper 11, 25 Jul 2022, 11 Apr 2023, 6 Apr 2024, 3 Apr 2025, 23 Jan 2026 S1, 24 Jan 2026 S2, 2 Apr 2026 S1, 4 Apr 2026 S2. All 9 questions below, oldest first.

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  1. Question 1

    2021 Paper 11

    23
    The correct order of intensity of colour of [NiCl4]2−\left\lbrack NiCl_{4} \right\rbrack^{2 -}, [Ni(H2O)4]2+\left\lbrack Ni\left( H_{2}O \right)_{4} \right\rbrack^{2 +} and [Ni(CN)4]2−\left\lbrack Ni(CN)_{4} \right\rbrack^{2 -} is:

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  2. Question 2

    25 Jul 2022

    131
    The correct order of energy of absorption for the following metal complexes is A: [Ni(en)3]2+,B:[Ni(NH3)6]2+,C:[Ni(H2O)6]2+\left\lbrack Ni(en)_{3} \right\rbrack^{2 +},B:\left\lbrack Ni\left( NH_{3} \right)_{6} \right\rbrack^{2 +},C:\left\lbrack Ni\left( H_{2}O \right)_{6} \right\rbrack^{2 +}

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  3. Question 3

    11 Apr 2023

    126
    Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: [CoCl(NH3)5]2+\left\lbrack CoCl\left( NH_{3} \right)_{5} \right\rbrack^{2 +} absorbs at lower wavelength of light with respect to [Co(NH3)5(H2O)]3+\left\lbrack Co\left( NH_{3} \right)_{5}\left( H_{2}O \right) \right\rbrack^{3 +} Reason R: It is because the wavelength of the light absorbed depends on the oxidation state of the metal ion. In the light of the above statements, choose the correct answer from the options given below:

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  4. Question 4

    6 Apr 2024

    42
    Consider the following complexes. [CoCl(NH3)5]2+,        [Co(CN)6]3−\left\lbrack CoCl\left( NH_{3} \right)_{5} \right\rbrack^{2 +},\ \ \ \ \ \ \ \ \left\lbrack Co(CN)_{6} \right\rbrack^{3 -}, (A) (B)
    [Co(NH3)5(H2O)]3+, [Cu(H2O)4]2+\left\lbrack Co\left( NH_{3} \right)_{5}\left( H_{2}O \right) \right\rbrack^{3 +},\ \left\lbrack Cu\left( H_{2}O \right)_{4} \right\rbrack^{2 +}
    (C) (D) The correct order of A,B,CA,B,C and DD in terms of wavenumber of light absorbed is:

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  5. Question 5

    3 Apr 2025

    39
    The correct order of the complexes [Co(NH3)5(H2O)]3+\left\lbrack Co\left( NH_{3} \right)_{5}\left( H_{2}O \right) \right\rbrack^{3 +} (A),  [Co(NH3)6]3+\ \left\lbrack Co\left( NH_{3} \right)_{6} \right\rbrack^{3 +}(B), [Co(CN)6]3−(C)\left\lbrack Co(CN)_{6} \right\rbrack^{3 -}(C) and [CoCl(NH3)5]2+(D)\left\lbrack CoCl\left( NH_{3} \right)_{5} \right\rbrack^{2 +}(D) in terms of wavelength of light absorbed is :

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  6. Question 6

    23 Jan 2026 S1

    34
    Given below are two statements : Statement I: [CoBr4]2−\left\lbrack {CoBr}_{4} \right\rbrack^{2 -} ion will absorb light of lower energy than [CoCl4]2−\left\lbrack {CoCl}_{4} \right\rbrack^{2 -} ion. Statement II : In [CoI4]2−\left\lbrack {CoI}_{4} \right\rbrack^{2 -} ion, the energy separation between the two set of d-orbitals is more than [CoCl4]2−\left\lbrack {CoCl}_{4} \right\rbrack^{2 -} ion. In the light of the above statements, choose the correct answer from the options given below :

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  7. Question 7

    24 Jan 2026 S2

    32
    The wavelengths of light absorbed by the following complexes are in the order: (I) [Co(NH3)6]3+\left\lbrack Co\left( NH_{3} \right)_{6} \right\rbrack^{3 +}; (II) [Co(H2O)6]3+\left\lbrack Co\left( H_{2}O \right)_{6} \right\rbrack^{3 +}; (III) [Co(CN)6]3−\left\lbrack Co(CN)_{6} \right\rbrack^{3 -}; (IV) [Co(NH3)5(H2O)]3+\left\lbrack Co\left( NH_{3} \right)_{5}\left( H_{2}O \right) \right\rbrack^{3 +}; (V) [CoF6]3−\left\lbrack CoF_{6} \right\rbrack^{3 -}

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  8. Question 8

    2 Apr 2026 S1

    37
    Match List-I with List-II. (en = ethylenediamine)
    List-I Chromium(III) complexList-II Δ0\Delta_{0} (cm−1cm^{- 1})
    (A)[Cr(CN)6]3−\left\lbrack Cr(CN)_{6} \right\rbrack^{3 -}(I)15,060
    (B)[CrF6]3−\left\lbrack {CrF}_{6} \right\rbrack^{3 -}(II)17,400
    (C)[Cr(H2O)6]3+\left\lbrack Cr\left( H_{2}O \right)_{6} \right\rbrack^{3 +}(III)22,300
    (D)[Cr(en)3]3+\left\lbrack Cr(en)_{3} \right\rbrack^{3 +}(IV)26,600
    Choose the correct answer from the options given below :

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  9. Question 9

    4 Apr 2026 S2

    35
    Consider the metal complexes [Ni(en)3]2+(A)\left\lbrack Ni(en)_{3} \right\rbrack^{2 +}(A), [NiCl4]2−(B)\left\lbrack NiCl_{4} \right\rbrack^{2 -}(B) and [Ni(NH3)6]2+(C)\left\lbrack Ni\left( NH_{3} \right)_{6} \right\rbrack^{2 +}(C). Choose the CORRECT option by considering the number of unpaired electron present in (A), (B) and (C) respectively and the order of frequency of absorption.

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