Q9 / 160 · AP EAMCET 2004 · Chemistry

Which of the following pairs of ions are colourless?

  • A
    $\mathrm{Ti}^{3+}, \mathrm{Cu}^{2+}$
  • Correct answer
    B
    $\mathrm{Sc}^{3+}, \mathrm{Zn}^{2+}$
  • C
    $\mathrm{Co}^{2+}, \mathrm{Fe}^{3+}$
  • D
    $\mathrm{Ni}^{2+}, \mathrm{V}^{3+}$

Solution

$$ \mathrm{Sc}^{3+}=[\mathrm{Ar}] 3 d^0, \mathrm{Zn}^{2+}=[\mathrm{Ar}] 3 s^{10} $$ Both of these ions have no unpaired electron, hence these are colourless.

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

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