Chemistry - Salt Analysis Question with Solution | TestHub
A mixture contains a Reddish Brown metallic oxide (A) and a yellow crystalline salt (B) . When the mixture is treated with dilute sulphuric acid, it yields a clear acidic filtrate along with a yellow insoluble residue (B) .
The filtrate is divided into two equal portions.
• The first portion, on treatment with aqueous potassium ferrocyanide solution , produces a blue precipitate (C) .
• The second portion, on addition of ammonium thiocyanate ,develops a blood-red coloration .
The insoluble residue (B) is found to be :
• Insoluble in excess aqueous ammonia ,
• But readily soluble in potassium cyanide solution as well as in sodium thiosulphate solution . Furthermore, the sodium extract of the original mixture, when treated with chlorine water, yields a brown solution . On shaking this solution with chloroform, the organic layer turns violet.
Identify the substances , and and calculate sum of number of atoms per formula unit of .
Answer:
Solution:
* Substance A is Fe₂O₃ (Reddish-brown oxide whose Fe³⁺ ions give a blood-red color with thiocyanate), containing 5 atoms.
* Substance B is AgI (Yellow crystalline salt insoluble in ammonia but soluble in thiosulphate; iodide is confirmed by the violet layer test), containing 2 atoms.
* Substance C is Fe₄[Fe(CN)₆]₃ (The Prussian blue precipitate formed from the reaction of Fe³⁺ with potassium ferrocyanide), containing 43 atoms.
* The sum of the number of atoms per formula unit of A, B, and C is: .
