The electrolytic bath used in gold plating of copper articles contains — Electrochemistry Chemistry Question

💡 Solution & Explanation

To achieve a smooth, even, and adherent layer of gold, the concentration of free $Au^+$ ions in the bath must be kept very low. This is achieved by using a complex cyanide salt of gold, typically formed by dissolving $AuCl_3$ in an excess of $NaCN$ to yield sodium dicyanoaurate(I). Therefore, correct answer is D.