(a) Complete the following chemical reaction equations :
(i) `Fe_((aq))^(2+) + MnO_(4 (aq))^(-) + H_((aq))^(+) to `
(ii) `Cr_(2)O_(7 (aq))^(2-) + I_((aq))^(-) + H_((aq))^(+) to`
(b) Explain the following observations :
(i) Transition elements are known to form many interstitial compounds .
(ii) With the same `d^(4)` d-orbital configuration `Cr^(2+)` ion is reducing while `Mn^(3+)` ion is oxidising .
(iii) The enthalpies of atomisation of the transition elements are quite high.

Explanation

`5Fe_((aq))^(2+) + MnO_(4 (aq))^(-) + 8H_((aq))^(+) to Mn_((aq))^(2+) + 4H_(2)O(l) + 5Fe_((aq))^(3+)`
(ii) `Cr_(2)O_(7 (aq))^(2-) + 6I_((aq))^(-) + 14H_((aq))^(+) to 2 Cr_((aq))^(3+) + 7H_(2)O(l) + 3I_(2)(g)`
b (i) The transition metals form a larger number of interstitial compounds in which small atoms such a hydrogen , carbon , boron and nitrogen occupy the empty spaces (interstitial sites ) in their lattices .
(iii) Due to the presence of large number of unpaired electrons in their atom, they form strong interatomic metallic bonds . Hence they have high enthalpies of atomisation .