Q27 / 100 · BITSAT 2024 (Memory Based Paper 1) · Chemistry

Which of the following complexes will exhibit maximum attraction to an applied magnetic field?

  • A
    $\left[\mathrm{Zn}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$
  • Correct answer
    B
    $\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$
  • C
    $\left[\mathrm{Co}(\mathrm{en})_3\right]^{3+}$
  • D
    $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$

Solution

Complex with maximum number of unpaired electron will exhibit maximum attraction to an applied magnetic field. $\left[\mathrm{Zn}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+} \rightarrow \mathrm{d}^{10}$ system $\rightarrow \mathrm{t}_{2 \mathrm{~g}}^6 \mathrm{e}_{\mathrm{g}}^4$ 0 unpaired $\mathrm{e}^{-}$ $\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+} \rightarrow \mathrm{d}^7$ system $\rightarrow \mathrm{t}_{2 \mathrm{~g}}^{5} \mathrm{e}_{\mathrm{g}}^2$ 3 unpaired $\mathrm{e}^{-}$ $\left[\mathrm{Co}(\mathrm{en})_3\right]^{3+} \rightarrow \mathrm{d}^6$ system $\rightarrow \mathrm{t}_{2 \mathrm{~g}}^6 \mathrm{e}_{\mathrm{g}}^0$ 0 unpaired $\mathrm{e}^{-}$ $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+} \rightarrow \mathrm{d}^8$ system $\rightarrow \mathrm{t}_{2 \mathrm{~g}}^{6} \mathrm{e}_{\mathrm{g}}^2$ 2 unpaired e

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

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