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Question
Account for the following:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
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Solution 1
In case of Mn '+2' oxidation state is more stable than '+3' oxidation state and in case of Cr '+3' oxidation state is more stable than '+2' oxidation state.
Solution 2
The E° value for the Mn3+/Mn2+ couple is much more positive than that for the Cr3+/Cr2+ couple. This is because the Mn2+ ion is particularly stable due to the extra stability of its half-filled valence electronic configuration (3d5). Thus Mn3+ ion has a very high tendency to gain an electron and form the much more stable Mn2+ ion.
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