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The D-And-f-Block Elements

Question
CBSEENCH12007114
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For M2+/M and M3+/M2+ systems the E° values for some metals are as follows:
Cr2+/Cr – 0.9 V Cr3+/Cr2+ – 0.4 V
Mn2+/Mn – 1.2 V Mn3+/Mn2+ + 1.5 V
Fe2+/Fe – 0.4 V Fe3+/Fe2+ + 0.8 V
Use this data to comment upon
(a)    The stability of Fe3+ in acid solution as compared to that of Cr3+ or Mn3+ and
(b)    In case with which iron can be oxidised as compared to the similar process for either chromium or manganese metal

Solution
We know that higher the reduction potential of a specie, there is larger tendency for its reduction to take place. Let us represent the reduction potentials i.e., E° values of three M3+/M2+ systems on number line.

Cr3+ /Cr2+ =-0.4V
Fe3+/Fe2+ =0.8V
Mn3+/Mn2+ =1.5V

Fom values of reduction potentials, it is clear that the stability of Fe3+ in acid solution is more than that Cr3+ but less than that of Mn3+.

b) Mn2+/Mn =-1.2V
    Cr2+/Cr =-0.9V
    Fe2+/Fe =-0.4V

The lower the reduction potential of a species, its oxidation will take place more readily.

∴  Mn is oxidised most readily to Mn2+ and Fe is oxidised least readily among given metals Mn, Cr and Fe.

Some More Questions From The d-And-f-Block Elements Chapter

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Which is a stronger reducing agent Cr2+ or Fe2+ and why?

Explain why Cu+ ion is not stable in aqueous solutions?

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

The outer electronic configuration of copper is 3d10 4s1, yet it is considered transition element. Why?

Why the melting points of transition elements are high?

Why Zn, Cd and Hg are not regarded as transition elements?

Name the first element of 3rd transition series.

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