In the silver plating of copper, $\mathrm{K}\left[\mathrm{Ag}\left(\mathrm{CN}_2\right]\right.$ is used…

In the silver plating of copper, $\mathrm{K}\left[\mathrm{Ag}\left(\mathrm{CN}_2\right]\right.$ 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 $\mathrm{Ag}$ from $\left[\mathrm{Ag}\left(\mathrm{CN}_2\right]^{-}\right.$ ion

Solution

Copper being more electropositive readily precipitate silver from their salt \(\left(\mathrm{Ag}^{+}\right)\) solution.
\(\mathrm{Cu}+2 \mathrm{AgNO}_3 \rightarrow \mathrm{Cu}\left(\mathrm{NO}_3\right)_2+\mathrm{Ag}\)
In \(\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_2\right]\) solution a complex anion \(\left[\mathrm{Ag}(\mathrm{CN})_2\right]\) is formed so \(\mathrm{Ag}^{+}\) ions are less available in the solution and Cu cannot displace Ag from this complex ion.

Asked in: NEET 2002

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