Statement-I : \(E^{0}\) value of the \(Mn^{3+}/Mn^{2+}\) couple is much more positive than that of \(Cr^{3+}/Cr^{2+}\)
Statement-II :\(Mn^{+2}(d^{5}\)) is more stable than \(Cr^{+2}(d^{4})\)

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+)

.Assertion : \(E^{0}\) for \(Mn^{3+}/Mn^{2+}\) couple is more positive than for \(Fe^{3+}/Fe^{2+}\) Reason :\(Mn^{3+}\) has \(d^{4}\) configuration and \(Fe^{3+}\) has a \(d^{5}\)configuration. (a) If both (A) and (R ) are correct and (R ) is the correct explanation of (A). (b) If both (A) and (R) are correct and (R) is the correct explanation of (A). (c) If (A) is correct,but (R) is incorrect. (d) If (A) is incorrect,but (R) is correct.

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

Assign reasons for the following : (i) The enthalpies of atomisation of transition elements are high. (ii) The transition metals and many of their compounds act as good catalyst. (iii) From element to element the actinoid contraction is greater than the lanthanoid contraction. (iv) The E^(@) value for the Mn^(3+)//Mn^(2+) couple is much more positive than that for Cr^(3+)//Cr^(2+) . (v) Scandium (Z = 21) does not exhibit variable oxidation states and yet it is regarded as transition element.

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

Assertion : E^@ value of Mn^(3+) | Mn^(2+) is more positive than for Cr^(3+)| Cr^(2+) . Reason Cr^(3+) is more stable than Cr^(2+) but Mn^(3+) is less stable than Mn^(2+) .

Wxplain why E^(@) for Mn^(3+)//Mn^(2+) couple is more positive than that for Fe^(3+)//Fe^(2+) (At. Nos. Mn=25,Fe=26)?

(a) Account for the following: (i) Manganese shows maximum number of oxidation states in 3d series? (ii) E^@ value for Mn^(3+)| Mn^(2+) couple is much more positive than that of Cr^(3+)| Cr^(2+) . (iii) Ti^(4+) is colourless whereas V^(4+) is coloured in an aqueous solution. (b) Write the chemical equations for the preparation of KMnO_4 from MnO_2 . Why does purple colour of acidified permanganate solution decolourise when it oxidise Fe^(2+) to Fe^(3+) .