Q30 / 160 · AP EAMCET 2023 (19 May Shift 1) · Chemistry

Match the following \begin{array}{lll} & \begin{array}{l} List I \\ (Complex) \end{array} & \begin{array}{l} List II \\ (Color) \end{array} \\ A. \left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+} & I. & Green \\ B. \left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_4(\mathrm{en})\right]^{2+} & II. Blue \\ C. \left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+} & III. Pale blue \\ D. \left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6(\mathrm{en})_2\right]^{2+} & IV. Violet \end{array}

  • A
    A-IV, B-I, C-III, D-II
  • B
    A-I, B-II, C-III, D-IV
  • Correct answer
    C
    A-IV, B-III, C-I, D-II
  • D
    A-I, B-III, C-II, D-IV

Solution

The splitting energy order is (due to strong-field ligand 'en') :- $$ \left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+} < \left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_4(\mathrm{en})\right]^{2+} < \left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_2(\mathrm{en})_2\right]^{2+} < $$ $\left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+}$ Thus, the colour shifts from large wave length to short or small frequency to high frequency which is from green to pale blue to blue to violet.

Hence, the correct answer is option: 'C'.

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