Chemistry-
General
Easy
Question
Metallic gold frequently is found in aluminosilicate rocks and it is finely dispersed among other minerals. It may be extracted by treating the crushed rock with aerated sodium cyanide solution. During this process metallic gold is slowly converted to 
, which is soluble in water. After equilibrium has been reached, the aqueous phase is pumped off and the metallic gold is recovered from it by reacting the gold complex with zinc, which is converted to 
Gold in nature is frequently alloyed with silver which is also oxidised by aerated sodium cyanide solution.
There have been several efforts to develop alternative gold extraction processes which could replace this one. Why ?
- Sodium cyanide solutions corrode mining machinery
- Sodium cyanide escapes into ground water and produces hydrogen cyanide which is toxic to many animals.
- Gold obtained by this process is not pure.
- The amount of gold in aluminosilicate rocks is very less.
The correct answer is: Sodium cyanide escapes into ground water and produces hydrogen cyanide which is toxic to many animals.
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