Logo
Jeeify
MCQMediumJEE 2023Crystal Field Theory

JEE Chemistry 2023 Question with Solution

Match List I with List II:

A matching table with List I as coordination entities A to D and List II as wavelength values in nm labeled I to IV.
  • A

    A-IV, B-I, C-III, D-II

  • B

    A-III, B-II, C-I, D-IV

  • C

    A-III, B-I, C-II, D-IV

  • D

    A-II, B-III, C-IV, D-I

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: Match the coordination entities with the wavelength of light absorbed.

Find: The correct correspondence between List I and List II.

From the extracted solution table:

  • A = [CoCl(NH3)5]2+[CoCl(NH_3)_5]^{2+} matches III = 535535
  • B = [Co(NH3)6]3+[Co(NH_3)_6]^{3+} matches II = 475475
  • C = [Co(CN)6]3−[Co(CN)_6]^{3-} matches I = 310310
  • D = [Cu(H2O)4]2+[Cu(H_2O)_4]^{2+} matches IV = 600600

Also, the solution uses:

E=hcλE = \frac{hc}{\lambda}

So,

E∝1λE \propto \frac{1}{\lambda}

Hence the crystal field splitting energy is inversely proportional to the absorbed wavelength, and stronger ligands correspond to larger splitting and smaller absorbed wavelength.

Therefore, the correct matching is A-III, B-II, C-I, D-IV.

The correct option is A.

Ligand Strength and Absorption Trend

Given: E=hcλE = \frac{hc}{\lambda} and therefore absorbed energy increases as wavelength decreases.

Find: Which wavelength corresponds to each coordination entity.

Among the ligands present, CN−CN^- is the strongest field ligand, so [Co(CN)6]3−[Co(CN)_6]^{3-} should absorb the smallest wavelength, which is 310 nm310 \, \text{nm}.

Aqua ligand is relatively weak field, so [Cu(H2O)4]2+[Cu(H_2O)_4]^{2+} corresponds to the largest wavelength, which is 600 nm600 \, \text{nm}.

The remaining values from the provided solution table are:

  • [CoCl(NH3)5]2+→535 nm[CoCl(NH_3)_5]^{2+} \rightarrow 535 \, \text{nm}
  • [Co(NH3)6]3+→475 nm[Co(NH_3)_6]^{3+} \rightarrow 475 \, \text{nm}

Thus,

  • A-III
  • B-II
  • C-I
  • D-IV

So the correct option is A. Note that this conclusion follows the solution and differs from the answer key.

Common mistakes

  • Assuming larger absorbed wavelength means larger crystal field splitting. This is wrong because E=hcλE = \frac{hc}{\lambda}, so larger splitting corresponds to smaller wavelength. Compare energies inversely with wavelength.

  • Ignoring the spectrochemical series. This is wrong because ligand strength determines crystal field splitting. Use the relative field strengths such as CN−CN^- being stronger than NH3NH_3, and H2OH_2O being weaker.

  • Following the answer key key without checking the worked solution. Here the provided solution table explicitly gives the mapping. Always prioritize the actual solution working when there is a conflict.

Practice more Crystal Field Theory questions

Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.

Start free trialMore on Crystal Field Theory

Related questions