Aqueous solution of a salt 'A', when mixed with NaoH solution and warmed, a black precipitate is formed. Black ppt. is filtered and dissolved in dil. H_(2)SO_(4) solution. The resulting solution gives a chocolate coloured precipitate with potassium ferrocyanide solution. the filtrate obtained after filtering off the black precipitate, upon warming with Zn and NaOH evolves a pungent smelling gas. the resulting solution also responds to the ring test. the filtrate does not evolve any gas when it is boiled with urea in the presence of H_(2)SO_(4). Q. The chocolate coloured precipitate is:

Aqueous solution of a salt 'A', when mixed with NaoH solution and warm

1.	Aqueous solution of a salt 'A', when mixed with NaoH solution and warmed, a black precipitate is formed. Black ppt. is filtered and dissolved in dil. H_(2)SO_(4) solution. The resulting solution gives a chocolate coloured precipitate with potassium ferrocyanide solution. the filtrate obtained after filtering off the black precipitate, upon warming with Zn and NaOH evolves a pungent smelling gas. the resulting solution also responds to the ring test. the filtrate does not evolve any gas when it is boiled with urea in the presence of H_(2)SO_(4). Q. The chocolate coloured precipitate is:
Answer» `Fe_(2)[Fe(CN)_(6)]` `Cu_(2)[Fe(CN)_(6)]` `HgSO_(4)` `[Fe(H_(2)O)_(5)(NO)]SO_(4)` SOLUTION :`CuO+H_(2)SO_(4) to CuSO_(4)+H_(2)S` `2CuSO_(4)+K_(4)[Fe(CN)_(6)] to underset("chocolate ppt.")(Cu_(2)[Fe(CN)_(6)]darr)+2K_(2)SO_(4)`