Q71 / 180 · NEET 2017 · Chemistry

Extraction of gold and silver involves leaching with CN- ion. Silver or gold is later recovered by:

  • A
    Liquation
  • B
    Distillation
  • C
    Zone refining
  • Correct answer
    D
    Displacement with Zn

Solution

Zinc metal can displace Ag and Au as Zn being more reactive than Ag and Au. The following reactions are involved in the extraction of gold or silver from their native ores. 

From Native ore,

4 Ag + 8 NaCN + 2 H 2 O + O 2 → Leaching 4 Na Ag CN 2 +    4 NaOH Soluble Sodium dicyanoargentate (I)

2 Na Ag CN 2 + Zn → Displacement Na 2 Zn CN 4 + 2 Ag ↓

Hence, the correct answer is option: 'D'.

Relevant Questions