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प्रश्न
Account for the following:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
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उत्तर १
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.
उत्तर २
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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संबंधित प्रश्न
Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?
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| Metallic radii/pm | 126 | 125 | 125 | 128 |
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| Column I (Catalyst) | Column II (Process) |
| (i) \[\ce{Ni}\] in the presence of hydrogen | (a) Zieglar Natta catalyst |
| (ii) \[\ce{Cu2C12}\] | (b) Contact process |
| (iii) \[\ce{V2O5}\] | (c) Vegetable oil to ghee |
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| (v) \[\ce{TiCl4 + Al (CH3)3}\] | (e) Haber's Process |
| (f) Decomposition of KCIO3 |
For M2+/M and M3+/M2+systems, the EΘ values for some metals are as follows:
| Cr2+/Cr | −0.9 V |
| Mn2+/Mn | −1.2 V |
| Fe2+/Fe | −0.4 V |
| Cr3/Cr2+ | −0.4 V |
| Mn3+/Mn2+ | +1.5 V |
| Fe3+/Fe2+ | +0.8 V |
Use this data to comment upon:
The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
