For M2+/M and M3+/M2+ systems, the E⊖ values for some metals are as follows:
Cr2+/Cr -0.9V
Cr3/Cr2+ -0.4 V
Mn2+/Mn -1.2V
Mn3+/Mn2+ +1.5 V
Fe2+/Fe -0.4V
Fe3+/Fe2+ +0.8 V
Use this data to comment upon:
(i) The stability of Fe3+in acid solution as compared to that of Cr3+or Mn3+ and
(ii) The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
(i) The E⊖ value for Fe3+/Fe2+ is higher than that for Cr3+/Cr2+and lower than that for Mn3+/Mn2+. So, the reduction of Fe3+to Fe2+is easier than the reduction of Mn3+to Mn2+, but not as easy as the reduction of Cr3+ to Cr2+. Hence, Fe3+is more stable than Mn3+, but less stable than Cr3+. These metal ions can be arranged in the increasing order of their stability as: Mn3+< Fe3+< Cr3+
(ii) The reduction potentials for the given pairs increase in the following order.
Mn2+ / Mn < Cr2+ / Cr < Fe2+ /Fe
So, the oxidation of Fe to Fe2+is not as easy as the oxidation of Cr to Cr2+and the oxidation of Mn to Mn2+. Thus, these metals can be arranged in the increasing order of their ability to get oxidised as: Fe < Cr < Mn value for Fe3+/ Fe2+ is higher than that for Cr3+/Cr2+and lower than that for Mn3+/Mn2+. So, the reduction of Fe3+to Fe2+is easier than the reduction of Mn3+to Mn2+, but not as easy as the reduction of Cr3+ to Cr2+. Hence, Fe3+is more stable than Mn3+, but less stable than Cr3+. These metal ions can be arranged in the increasing order of their stability as: Mn3+< Fe3+< Cr3+ (ii) The reduction potentials for the given pairs increase in the following order. Mn2+ / Mn < Cr2+ / Cr < Fe2+ /Fe So, the oxidation of Fe to Fe2+is not as easy as the oxidation of Cr to Cr2+and the oxidation of Mn to Mn2+. Thus, these metals can be arranged in the increasing order of their ability to get oxidised as: Fe < Cr < Mn
The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:
| Experiment |
A/ mol L - 1 |
B/ mol L - 1 |
Initial rate/mol L - 1 min - 1 |
| I | 0.1 | 0.1 |
2.0 × 10 - 2 |
| II | -- | 0.2 |
4.0 × 10 - 2 |
| III | 0.4 | 0.4 | -- |
| IV | -- | 0.2 |
2.0 × 10 - 2 |
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(i) The E⊖ value for Fe3+/Fe2+ ­­ is higher than that for Cr3+/Cr2+and lower than that for Mn3+/Mn2+. So, the reduction of Fe3+to Fe2+is easier than the reduction of Mn3+to Mn2+, but not as easy as the reduction ...
Step-by-step explanation:
• (i) The E⊖ value for Fe3+/Fe2+ ­­ is higher than that for Cr3+/Cr2+and lower than that for Mn3+/Mn2+
• So, the reduction of Fe3+to Fe2+is easier than the reduction of Mn3+to Mn2+, but not as easy as the reduction of Cr3+ to Cr2+
• Hence, Fe3+is more stable than Mn3+, but less stable than Cr3+
• These metal ions can be arranged in the increasing order of their stability as: Mn3+< Fe3+< Cr3+
•
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