The correct answer is A. Gold chloride.
Gold chloride is a chemical compound with the formula AuCl3. It is a yellow, water-soluble solid that is used in electroplating, photography, and as a catalyst. Gold chloride is prepared by dissolving gold in aqua regia, which is a mixture of nitric acid and hydrochloric acid.
Gold nitrate is a chemical compound with the formula Au(NO3)3. It is a yellow, water-soluble solid that is used in electroplating, photography, and as a catalyst. Gold nitrate is prepared by dissolving gold in nitric acid.
Gold sulphate is a chemical compound with the formula Au2(SO4)3. It is a yellow, water-soluble solid that is used in electroplating, photography, and as a catalyst. Gold sulphate is prepared by dissolving gold in sulphuric acid.
Potassium aurocyanide is a chemical compound with the formula K[Au(CN)2]. It is a yellow, water-soluble solid that is used in electroplating, photography, and as a catalyst. Potassium aurocyanide is prepared by dissolving gold in potassium cyanide.
In electroplating, a metal is deposited on a surface by passing an electric current through a solution containing ions of the metal to be deposited. The metal ions are attracted to the cathode, where they are reduced to the metal. The anode, which is made of the same metal as the cathode, is dissolved, providing more metal ions for the solution.
The electrolyte used in electroplating must be a good conductor of electricity and must contain ions of the metal to be deposited. Gold chloride, gold nitrate, gold sulphate, and potassium aurocyanide are all good conductors of electricity and contain ions of gold. However, gold chloride is the most commonly used electrolyte in electroplating because it is the most stable and least expensive.