(i) Write the balanced equations to represent what happens when
(a) acidified potassium permanganates reacts with hydrogen sulphide ?
(b) acidified potassium dichromate solution reacts with iron (II) solution (ionic equation) ?
(ii) The figure given below illustrates the first ionisation enthalpies of first, second and third series of transition elements.

(a) Which series amongst the first, second and third series of transition elements have the highest first ionisation enthalpy and Why ?
(b) Why there is a fall in `IE_(2)` from Cr to Mn and from Cu to Zn ? Explain.