Aqueous solution of a salt 'A'

CHEMISTRY · Single correct · GCSE · Chemistry · Chemical Analysis · Chemical Analysis

Problem

Aqueous solution of a salt 'A', when mixed with

\text{NaOH}

solution and warmed, a black precipitate is formed. Black ppt. is filtered and dissolved in dil.

\text{H}_2\text{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

\text{Zn}

and

\text{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

\text{H}_2\text{SO}_4

. The chocolate coloured precipitate is: (1)

\text{Fe}_2[\text{Fe}(\text{CN})_6]

(2)

\text{Cu}_2[\text{Fe}(\text{CN})_6]

(3)

\text{HgSO}_4

(4)

[\text{Fe}(\text{H}_2\text{O})_5(\text{NO})]\text{SO}_4

Related theory

Qualitative Analysis
Alkalis on metals and oxides

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