Metallic gold is collected from below the anode when a mixture of copper and gold metals is refined by electrolysis. Explain this behavior.

Electrolysis is a process that uses an electric current to drive a non-spontaneous chemical reaction. In the case of refining metals, this will involve the dissolution of the metal at the anode (positive electrode) and its deposition at the cathode (negative electrode). This is done in an electrolyte solution which facilitates the flow of ions between the electrodes.

Both copper and gold are metals that have positive redox potentials, which means they are generally more resistant to oxidation (loss of electrons) and more likely to undergo reduction (gain of electrons). In an electrolytic cell, the metal that has the highest redox potential will have the greatest tendency to be reduced at the cathode, while the metal with the lower redox potential will oxidize more readily at the anode.

Although both copper and gold have positive redox potentials, gold has a higher redox potential than copper. Gold has a reduction potential of +1.50 V while copper has a reduction potential of +0.337 V. This means gold is less prone to oxidation and more prone to reduction than copper.

Based on the redox potentials, when a mixture of copper and gold is subjected to electrolysis, copper is more likely to be oxidized at the anode compared to gold. This is because copper has a lower redox potential, therefore it will readily lose electrons to form Cu(2+) ions in the electrolyte. At the cathode, gold ions will be more likely to undergo reduction due to their higher redox potential. However, when copper ions are present in the solution, they will preferentially reduce at the cathode, forming copper metal. As a result, gold ions will not efficiently deposit onto the cathode and will instead remain in the electrolyte solution. Since gold has a higher density than the electrolyte solution, the gold ions in the solution will gradually settle down due to gravity, forming a layer of metallic gold below the anode. So in conclusion, metallic gold is collected from below the anode during the electrolysis of a mixture of copper and gold because of the differences in the redox potentials between the two metals. Copper is more likely to be oxidized at the anode and reduced at the cathode, while gold remains in the electrolyte solution and eventually settles down due to its higher density.