Chemistry - Metallurgy Question with Solution | TestHub

(2) $\stackrel{+2}{\mathrm{PbS}{\mathrm{O}}_4}+\stackrel{+2}{\mathrm{Pb}}\stackrel{-2}{S}\to \stackrel{0}{\mathrm{Pb}}+\stackrel{+4}{2\mathrm{S}}$O₄

So the given reaction is self-reduction.

(3) Ag ore $+{\mathrm{CN}}^{\ominus }\stackrel{{\mathrm{O}}_2}{\to }\mathrm{Na}\left[\mathrm{Ag}(\mathrm{CN}{)}_2\right]$

(This is a leaching process.) The given reaction is a reduction reaction by Zn.

(4) Reduction potential

$$E_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}^{\circ }>E_{{\mathrm{Cu}}^{+2}/\mathrm{Cu}}^{\circ }$$

So, displacement of ${\mathrm{Cu}}^{+2}$ is not possible by ${\mathrm{Ag}}^{+}$.