General Principles And Processes Of Isolation Of Elements Ques 17
17. Extraction of gold and silver involves leaching with $CN^{-}$ion. Silver is later recovered by
[2017]
(a) distillation
(b) zone refining
(c) displacement with $Zn$
(d) liquation
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Answer:
Correct Answer: 17.(c)
Solution:
- (c) $Zn$ being more reactive than $Ag$ and $Au$, displaces them.
$4 Ag+8 NaCN+2 H_2 O+O_2 \xrightarrow{\text{ Leaching }} 4 Na[Ag(CN)_2]+4 NaOH$
Soluble Sodium dicyanoargentate $(I)$
Soluble cyanide compound can be treated with $Zn$ to give metal by displacement.
$ 2 Na[Ag(CN)_2]+Zn \xrightarrow {\text{ Displacement }} Na_2[Zn(CN)_4]+2 Ag \downarrow $
BETA
