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Question: The cyanide complex of silver formed in the silver extraction in Mac-Arthur’s Forrest cyanide proces...

The cyanide complex of silver formed in the silver extraction in Mac-Arthur’s Forrest cyanide process is:
A. [Ag(CN)2]−{[{\text{Ag(CN}}{{\text{)}}_2}]^ - }
B. K2[Ag(CN)3]{{\text{K}}_2}[{\text{Ag(CN}}{{\text{)}}_3}]
C. [Ag(CN)4]2−{[{\text{Ag(CN}}{{\text{)}}_4}]^{2 - }}
D. Na3[Ag(CN)4]{\text{N}}{{\text{a}}_3}[{\text{Ag(CN}}{{\text{)}}_4}]

Explanation

Solution

Mac-Arthur’s Forrest cyanide process is used for extracting gold or silver from its ore by dissolving the ore into the solution of potassium cyanide or sodium cyanide.

Complete step by step answer:
Let’s start with discussing the Mac-Arthur’s Forrest cyanide process first. This process is used for extracting gold or silver from its ore by dissolving the ore into the solution of potassium cyanide or sodium cyanide. The process is named after three chemists Robert W. Forrest, John S. MacArthur and William Forrest.
Coming to the process, this process contains three steps. In the first step, the finely grinded ore of the precious metal is brought in contact with a solution containing cyanide. In the second step the solids are separated from the clear solution and in the third step the precious metals are recovered from the solution by precipitating with zinc.
The reaction that follows the reaction is given below
At Cathode: [Ag(CN)2]−→Ag+ + 2CN−{{\text{[Ag(CN}}{{\text{)}}_{\text{2}}}{\text{]}}^ - } \to {\text{A}}{{\text{g}}^ + }{\text{ + 2C}}{{\text{N}}^ - }
At Anode: Zn + 2OH - →Zn(OH)2 + 2e - {\text{Zn + 2O}}{{\text{H}}^{\text{ - }}} \to {\text{Zn(OH}}{{\text{)}}_{\text{2}}}{\text{ + 2}}{{\text{e}}^{\text{ - }}}
Both these reactions happen and the Precious metal is obtained. Clearly the Cyanide complex of Silver is[Ag(CN)2]−{[{\text{Ag(CN}}{{\text{)}}_2}]^ - }.
Hence the answer to this question is option A. [Ag(CN)2]−{[{\text{Ag(CN}}{{\text{)}}_2}]^ - }

∴\therefore Option A is correct .

Note:
We also know that Mac-Arthur’s Forrest Cyanide process is used to extract precious metals like Gold and silver from their ore. It is a hydrometallurgical technique which first converts gold ore into water soluble coordinating complex. About 13%13\% of total cyanide is used for this process and rest is used in other industries like plastic, adhesive and pesticide. It is to be noticed that cyanide is a highly poisonous substance, so one should always handle cyanide with care.