NEET Solved Paper 2017 Question 37
Question: Extraction of gold and silver involves leaching with $ C{N^{-}} $ ion. Silver is later recovered by
Options:
A) Displacement with Zn
B) Liquation
C) Distillation
D) Zone refining
Show Answer
Answer:
Correct Answer: A
Solution:
Zn being more reactive than Ag and Au, displaces them.
From Native ore,
$ 4Ag+8NaCN+2H _2O+O _2\xrightarrow{Leaching} $ $ \underset{\begin{smallmatrix} \ Souble \\ Sodium\ \\ \ dicyanoargen\ late\ \text{(I)} \end{smallmatrix}}{\mathop{4Na[Ag{{(CN)}_2}]}}\ +4NaOH $ $ 2Na[Ag{{(CN)}_2}]+Zn\xrightarrow{Displaceement} $ $ Na _2[Zn{{(CN)}_4}]+2Ag\downarrow $
