Q20 / 110 · VITEEE 2022 · Chemistry

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

  • A
    A thin layer of \(\mathrm{Ag}\) is formed on \(\mathrm{Cu}\)
  • B
    More voltage is required
  • C
    \(\mathrm{Ag}^{+}\)ions are completely removed from solution
  • Correct answer
    D
    Less availability of \(\mathrm{Ag}^{+}\)ions, as Cu cannot displace \(\mathrm{Ag}\) from \(\left[\mathrm{Ag}(\mathrm{CN})_2\right]^{-}\)ion

Solution

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.

Hence, the correct answer is option: 'D'.

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