(a) What happens when
(i) Manganate ions `(MnO_(4)^(2-))` undergoes diSQProportionation reaction in acidic medium ?
(ii) Lanthanum is heated with Sulphur?
(b) Explain the following trends in the properties of the members of the First series of transition elements:
(i) ` E^(@) (M^(2+)//M)` value for copper is positive `(+ 0.34 V)` in contrast to the other members of the series.
(ii) `Cr^(2+)` is reducing while `Mn^(3+)` is oxidising, though both have `d^(4)` configuration.
(iii) The oxidising power in the series increases in the order `VO_(2)^(+) lt Cr_(2)O_(7)^(2-) lt MnO_94)^(-)`.