Miners obtain gold by soaking gold-containing ores in an aqueous solution of sod

Question

Miners obtain gold by soaking gold-containing ores in an aqueous solution of sodium cyanide. A very soluble complex ion of gold forms in the aqueous solution as a result of the redox reaction 4 Au(s) + 8 NaCN(aq) + 2 H2O(l) + O2(g) ---> 4 Na[Au(CN)2](aq) + 4 NaOH(aq) 1. What atomic species is being oxidized? 2. What atomic species is being reduced? 3..Gold miners then react the basic aqueous product solution with Zn dust to recover the gold metal. Write a balanced redox reaction for this recovery process with zinc.

Explanation / Answer

4 Au(s) + 8 NaCN(aq) + 2 H2O(l) + O2(g) ---> 4 Na[Au(CN)2](aq) + 4 NaOH(aq)
Gold is being oxidized, so O2 is being reduced.

In the last part, gold is being reduced, and zinc is being oxidized.

[Au(CN)2]- + Zn(s) ------> Au(s) + Zn2+ + CN-

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