The major product of the following reaction is :

A metal ‘M’ reacts with nitrogen gas to afford ‘M₃N’. ‘M₃N’ on heating at high temperature gives back ‘M’ and on reaction with water produces a gas ‘B’. Gas ‘B’ reacts with aqueous solution of CuSO₄ to form a deep blue compound. ‘M’ and ‘B’ respectively are :

What is the standard reduction potential (E^o) for Fe³⁺ $$ \to $$ Fe ?
Given that :
Fe²⁺ + 2e^$$-$$ $$ \to $$ Fe; $$E_{F{e^{2 + }}/Fe}^o$$ = $$-$$0.47 V
Fe³⁺ + e^$$-$$ $$ \to $$ Fe²⁺; $$E_{F{e^{3 + }}/F{e^{2 + }}}^o$$ = +0.77 V

sp³d² hybridization is not displayed by :