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.
Substance dissolved in HCl and a coloured solution is prepared. Calculate number of reagents that can convert this solution green.
Answer:
Solution:
Substance A is Fe₂O₃ (reddish-brown metallic oxide), which dissolves in HCl to form a yellow-brown solution containing Fe³⁺ ions.
To change the color of the solution to green, Fe³⁺ must be reduced to light-green Fe²⁺ ions.
Therefore, the selected substances must function as reducing agents.
The 7 reducing agents from the given options are:
* Tin(II) chloride
* Hydroxylamine + Hydrochloride
* Ascorbic acid
* Cadmium metal
* Sulfur dioxide
* Hydrazine / H⁺
* Zinc metal
Final Answer: 7
