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In the silver plating of copper, $\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]$ is used instead of $\mathrm{AgNO}_{3} .$ The reason is
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less availability of $\mathrm{Ag}^{+}$ions, as Cu cannot displace Ag from $\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-}$ion
In the silver plating of copper, $\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]$ is used instead of $\mathrm{AgNO}_{3}$. Copper being more electropositive readily precipitate silver from their salt solution
$$
\mathrm{Cu}+2 \mathrm{AgNO}_{3} \longrightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{Ag}
$$
whereas in $\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]$ solution a complex anion $\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-}$is formed and hence $\mathrm{Ag}^{+}$ are less available in the solution and therefore copper cannot displace $\mathrm{Ag}$ from its complex ion.
$$
\mathrm{Cu}+2 \mathrm{AgNO}_{3} \longrightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{Ag}
$$
whereas in $\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]$ solution a complex anion $\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-}$is formed and hence $\mathrm{Ag}^{+}$ are less available in the solution and therefore copper cannot displace $\mathrm{Ag}$ from its complex ion.
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