Question

The electrolytes usually used in the electroplating of gold and silver, respectively, are

• A. $\left[\right.Au\left(\right.OH\left(\left.\right)_{4}\left(\left]\right.\right)^{-}$ and $\left[\right.Ag\left(\right.OH\left(\left.\right)_{2}\left(\left]\right.\right)^{-}$
• B. $\left[\right.Au\left(\right.CN\left(\left.\right)_{2}\left(\left]\right.\right)^{-}$ and $\left[\right.AgCl_{2}\left]\right.^{-}$
• C. $\left[\right.Au\left(\right.NH_{3}\left(\left.\right)_{2}\left(\left]\right.\right)^{+}$ and $\left[\right.Ag\left(\right.CN\left(\left.\right)_{2}\left(\left]\right.\right)^{-}$
• D. $\left[\right.Au\left(\right.CN\left(\left.\right)_{2}\left(\left]\right.\right)^{-}$ and $\left[\right.Ag\left(\right.CN\left(\left.\right)_{2}\left(\left]\right.\right)^{-}$

Answer 1

Answer: (D)

Amine complexes of gold are not stable, so, they cannot be used as a solvent.Moreover, in electroplating with silver, silver cyanide is used as electrolyte because the cyanide ion, $CN^{-}$ , reacts with silver ion, $Ag^{+}$ to form the complex ion $Ag\left(\right.CN\left.\right)_{2}^{-}$ . This produces a silver and more adherent silver plating.