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AIIMS 201826 May
Exam
AIIMS
Year
2018
Date
26 May
Subject
Chemistry
Chapter
d and f Block Elements

AIIMS 2018 · 26 May · Chemistry · d and f Block Elements

Which is least stable in aqueous medium?

Which is least stable in aqueous medium?

Options

  1. AFe2+\mathrm{Fe}^{2+}
  2. BCo2+\mathrm{Co}^{2+}
  3. CNi2+\mathrm{Ni}^{2+}
  4. DMn2+\mathrm{Mn}^{2+}

Correct answer

A. Fe2+\mathrm{Fe}^{2+}

Step-by-step solution

\mathrm{Fe}^{2+}(3d6)\left(3 d^6\right) quickly oxidises to Fe3+\mathrm{Fe}^{3+} \left(3 d^5\right., more stable) in aqueous medium.
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