Question

Which process is used for extraction of Ag from silver coin?

• A. Prake process
• B. Cyanide process
• C. Froth flotation
• D. Monds process

Answer 1

The correct option is B Cyanide process

Reaction process:

Silver coin $(Cu+Ag)\stackrel{conc.HN{O}_3}{\to }\begin{array}{c}(C{u}^{2+}+A{g}^{+})N{O}_3^{-}\\ \downarrow NaCl\\ AgCl\downarrow (whiteppt.)\end{array}$ $2AgCl+N{a}_{2}C{O}_3\to A{g}_{2}C{O}_3+2NaCl$ $A{g}_{2}C{O}_3\stackrel{\Delta }{\to }2Ag\downarrow +C{O}_2\uparrow +\frac{1}{2}{O}_2\uparrow$

Also, we can use cyanide process with $AgCl$.

(Silver and gold are extracted by the cyanide process (Macarthur - Forrest process). After the preliminary crushing and concentration by froth floatation process, the ore (crushed auriferous rocks in the case of gold) is leached with dilute (0.4 - 7%) solution of sodium cyanide made alkaline by adding lime kept agitated by a current of air. Silver (or gold) pass into solution as argento cyanide (or aurocyanide):

$A{g}_{2}S+4NaCN\to 2Na\left[Ag\right(CN{)}_2]+N{a}_{2}S$

$2Ag(CN{)}_2^{–}+Zn\to Zn(CN{)}_4^{2–}+2Ag$)