Among the following complexes (K-P),

K₃[Fe(CN)₆] (K), [Co(NH₃)₆]Cl₃ (L), Na₃[Co(oxalate)₃] (M), [Ni(H₂O)₃]Cl₂ (N), K₂[Pt(CN)₄] (O) and [Zn(H₂O)₆(NO₃)₂] (P)

The diamagnetic complexes are

Passing H₂S gas into a mixture of Mn²⁺, Ni²⁺, Cu²⁺ and Hg²⁺ ions in an acidified aqueous solution precipitates

Amongst the compounds given, the one that would from a brilliant coloured dye on treatment with NaNO₂ in dil. HCl followed by addition to an alkaline solution of $$\beta$$-naphthlol is

Reduction of the metal centre in aqueous permanganate ion involves