A mixture of copper and gold metals that is subjected to electrorefining contains tellurium as an impurity. The standard reduction potential between tellurium and its lowest common oxidation state, Te4+, is Te4+1aq2 + 4 e- ¡ Te1s2 E°red = 0.57 V Given this information, describe the probable fate of tellurium impurities during electrorefining. Do the impurities fall to the bottom of the refining bath, unchanged, as copper is oxidized, or do they go into solution as ions? If they go into solution, do they plate out on the cathode?

Key Concepts

Electrorefining Process

Electrorefining is a method used to purify metals by using electrolysis. In this process, an impure metal is made the anode, and pure metal is deposited at the cathode. The impurities, depending on their solubility and electrochemical properties, can either remain in the solution or settle at the bottom. Understanding this process is crucial to predicting the behavior of impurities like tellurium during electrorefining.

Standard Reduction Potential

Standard reduction potential (E°red) is a measure of the tendency of a chemical species to gain electrons and be reduced. A higher E°red value indicates a greater likelihood of reduction occurring. In the context of tellurium, the given E°red of 0.57 V suggests that Te4+ ions can be reduced to solid tellurium, influencing whether tellurium will remain in solution or deposit on the cathode during electrorefining.

Behavior of Impurities in Electrolytic Solutions

The behavior of impurities in electrolytic solutions is determined by their solubility and electrochemical properties. Impurities can either dissolve as ions or precipitate out depending on their reduction potentials and interactions with the electrolyte. In the case of tellurium, its ability to exist as Te4+ ions means it may go into solution during electrorefining, potentially leading to its deposition on the cathode if conditions favor its reduction.