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MCQEasyJEE 2023Crystal Field Theory

JEE Chemistry 2023 Question with Solution

Which of the following is the correct order of ligand field strength?

  • A

    CO<en<NH3<C2O42−<S2−\mathrm{CO} < \mathrm{en} < \mathrm{NH_3} < \mathrm{C_2O_4^{2-}} < \mathrm{S^{2-}}

  • B

    S2−<C2O42−<NH3<en<CO\mathrm{S^{2-}} < \mathrm{C_2O_4^{2-}} < \mathrm{NH_3} < \mathrm{en} < \mathrm{CO}

  • C

    NH3<en<CO<S2−<C2O42−\mathrm{NH_3} < \mathrm{en} < \mathrm{CO} < \mathrm{S^{2-}} < \mathrm{C_2O_4^{2-}}

  • D

    S2−<NH3<en<CO<C2O42−\mathrm{S^{2-}} < \mathrm{NH_3} < \mathrm{en} < \mathrm{CO} < \mathrm{C_2O_4^{2-}}

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: The question asks for the correct increasing order of ligand field strength.

Find: The correct option using the spectrochemical series.

From the solution, the increasing order of ligand field strength is:

S2−<C2O42−<NH3<en<CO\mathrm{S^{2-} < C_2O_4^{2-} < NH_3 < en < CO}

Comparing this order with the given options shows that option B matches the spectrochemical series.

However, the solution explicitly states The Correct Option is D, which conflicts with the worked order shown in the same the solution. Since the working is the primary source, the defensible answer from the extracted order is B.

Therefore, the correct option is B.

Common mistakes

  • Using the listed final option label from the page without checking the worked spectrochemical series. The page says D, but the extracted order matches B. Always verify the sequence against the actual ligand order.

  • Placing CO\mathrm{CO} before weaker ligands incorrectly. CO\mathrm{CO} is a strong field ligand and appears toward the strong-field end of the spectrochemical series, not the weak-field end.

  • Confusing en\mathrm{en} and NH3\mathrm{NH_3}. Ethylenediamine is stronger than ammonia in the spectrochemical series, so en\mathrm{en} must come after NH3\mathrm{NH_3} in increasing field strength.

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