In the silver plating of copper, $\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_{2}ight]$ is used instead of…

In the silver plating of copper, $\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_{2}ight]$ is used instead of $\mathrm{AgNO}_{3}$. The reason is
  1. a thin layer of $\mathrm{Ag}$ is formed on $\mathrm{Cu}$
  2. more voltage is required
  3. $\mathrm{Ag}^{+}$ ions are completely removed from solution
  4. less availability of $\mathrm{Ag}^{+}$ ions, as $\mathrm{Cu}$ cannot displace Ag from $\left[\mathrm{Ag}(\mathrm{CN})_{2}ight]^{-}$ ion

Solution

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

Asked in: JEE-TOPICTESTS-CHEMISTRY

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