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The correct order of E° M2+/M values with negative sign for the four successive elements Cr, Mn, Fe and Co is

1. Mn > Cr > Fe > Co
2. Cr < Fe > Mn > Co
3. Fe > Mn > Cr > Co
4. Cr > Mn > Fe > Co

Correct answer: Mn > Cr > Fe > Co

Solution

The standard reduction potentials (E°) for these metals indicate their ability to gain electrons, with manganese having the highest tendency to be reduced, followed by chromium, iron, and cobalt. This order reflects their relative reactivity and stability in their ionic forms.

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