Silver ores and native gold have to be leached with metal cyanides. Suggest a reason for this.

Solution

Silver ores and native gold have to be leached with metal cyanides as these form water soluble complexes with sodium or potassium cyanide.

{Ag}_{2} S + 4 NaCN \to \underset{Soluble complex}{2 Na [Ag (CN)_{2}]} + {Na}_{2} S 8 Au + 8 NaCN + 2 H_{2} O \to \underset{Soluble complex}{4 Na [Au (CN)_{2}]} + 4 NaOH

From this silver can be precipitated by addition of more electropositive metal like Zn.

2Na[Ag(CN)₂] + Zn → 2Ag ↓ + Na₂ Zn(CN)₄2Na[Au(CN)₂] + Zn → 2Au↓ + Na₂ Zn(CN)₄

Some More Questions From General Principles And Processes of Isolation Of Elements Chapter

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General Principles And Processes Of Isolation Of Elements

Silver ores and native gold have to be leached with metal cyanides. Suggest a reason for this.

Some More Questions From General Principles And Processes of Isolation Of Elements Chapter

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