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Why is the value for (Mn^(3+))/(Mn^(2+))...

Why is the value for `(Mn^(3+))/(Mn^(2+))` couple much more positive than that for `(Cr^(3+))/(Cr^(2+))` or `(Fe^(3+))/(Fe^(2+))`? Explain

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Much larger third ionisation energy of Mn (where the required change is `d^(5)` to `d^(4)`) is mainly responsible for this. This also explains why the +3 state of Mn is of little importance.
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Why is the E^(Theta) value for the Mn^(3+)//Mn^(2+) couple much more positive than that for Cr^(3+)//Cr^(2+) or Fe^(3+)//Fe^(2+)

(a) why is the E^(Theta) value for the Mn^(3+)//Mn^(2+) couple much more positivethan that for Cr^(3+)//Cr^(2+) or Fe^(3+) // Fe^(2+) ? Explain. (b) What is meant by 'disproportionation' of an oxidation state? Give example.

S_(1) : Mn^(2+) compounds more stable than Fe^(2+) towards oxidation to their +3 state. S_(2) : Titanium and copper both in the first series of transition metals exhibits +1 oxidation state most frequently. S_(3) : Cu^(+) ions is stable in aqueous solutions. S_(4) : The E^(0) value for the Mn^(3+)//Mn^(2+) couple much more positive than that for Cr^(3+)//Cr^(2+) or Fe^(3+)//Fe^(2+) ,

Why is the E^(Theta) value for the Mn^(3+)//Mn^(2+) couple much postive than for Cr^(3+)//Cr^(2+) or Fe^(3+)//Fe^(2+) ? Example

How would you account for the following? (i)The atomic radii of the metals of the third (5d) series of trasition elements are virtually the same as those of the corresponding members of the second (4d) series. (ii)The E^(@) value for the Mn^(3+)//Mn^(2+) couple is much more positive than that for Cr^(3+)//Cr^(2+) couple or Fe^(3+)//Fe^(2+) couple. (iii)The highest oxidation state of a metal is exhibited in itsoxide or fluoride.

How would you account for the following? (i) The atomic radii of the metals of the third (5d) series of transition elements are virtually the same as those of the corresponding member of the second (4d) serie (ii) The E^(@) value for the Mn^(3+)//Mn^(2+) couple is much more positive than that for Cr^(3+)//Cr^(2+) couple of Fe^(3+)//Fe^(2+) couple. (iii) The highest oxidation state of a metal is exhibited in its oxides or fluoride.

E_(Mn^(3+)//Mn^(2+))^@ is highly positive than that of E_(Cr^(3+)//Cr^(2+))^@orE_(Fe^(3+)//Fe^(2+))^@ because

NCERT-THE D AND F BLOCK ELEMENTS-Exercise
  1. Why is the value for (Mn^(3+))/(Mn^(2+)) couple much more positive tha...

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  2. Write down the electronic configuration of: (i). Cr^(3+) (ii). Pm^...

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  3. Why are Mn^(2+) compounds more stable than Fe^(2+) toward oxidation to...

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  4. Explain briefly how +2 state become more and more stable in the first ...

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  5. To what extent do the electronic configurations, decide the stability ...

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  6. What may be the stable oxidation state of the transition element with ...

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  7. Name the oxometal anions of the first series of the transition metals ...

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  8. What is lanthanoid contraction? What are the consequences of lanthanol...

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  9. What are the characteristics of the transition elements and why are th...

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  10. In what way is the electronic configuration of the transition elements...

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  11. What are the different oxidation states exhibited by the lanthanoids?

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  12. Explain gives reason. (a) Transition metal and many of their compoun...

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  13. What are interstitial compounds? Why are such compounds well known for...

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  14. How is the variability in oxidation states of transition metals differ...

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  15. Describe the preparation of potassium dichromate from iron chromite or...

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  16. Describe the oxidising action of potassium dichromate and write the io...

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  17. Describe the preparation of potassium permanganate. How does the acidi...

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  18. For M^(2+)//M and M^(3+)//M^(2+) systems the E^(ϴ) values for some met...

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  19. Predict which of the following will be coloured in aqueous solution? ...

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  20. Compare the stability of +2 oxidation state for the elements of the fi...

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  21. Compare the chemistry of actinoids with that of the lanthanoids with s...

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