Question

When copper is purified by electrorefining process, noble metals like ${\text{Ag}}\;{\text{and Au}}$ are found in:
A) cathode mud
B) over anode
C) anode mud
D) over cathode or anode

Answer 1

Electrorefining is an electrochemical process. It includes the passage of electricity through a conducting solution through two electrodes. In this purifying process the impurities are left behind called “anode mud or slime.”

Complete step by step answer:
Electrorefining is an electrochemical process where we purify certain substances by passing electricity through their respective solutions by using the metal piece to be purified as the electrodes.
For an electrochemical process to occur, there is the need of certain things like a vessel, an electrolyte or the conducting solution, a cathode and an anode which are called the electrodes and a power source. The selection of the electrolyte and the electrodes depend upon the purpose of the process.
Here we are using an electrochemical process for the purification of the metal copper. So we are taking a piece of impure copper as the anode by connecting it to the positive terminal of the power source and a piece of pure copper, which will be a thin strip, as the cathode by connecting it to the negative terminal of the power source. The electrolyte we are choosing is the respective solution of the metal and that is the solution of ${\text{CuS}}{{\text{O}}_{\text{4}}}$.
When we pass electricity through the solution, copper from the anode gets deposited in the solution and from the solution, it moves on to the cathode, which is the thin strip of pure copper. This process is continuous and the impurities in the anode sometimes just adhere to the anode or otherwise it will fall to the bottom of the refining cell. These impurities are collectively called anode mud. It may include noble metals like ${\text{Ag}}\;{\text{and Au}}$.

Therefore, Option C is the correct answer

Note: Electrorefining is an efficient process in purifying many metals in the metallurgical processes. Electrochemical processes are also used in providing corrosion resistant coating over certain metals.
When the process of electrorefining of copper is over, we can see that the thin strip of pure copper at the cathode becomes thick. This is because of the fact that pure copper is deposited onto it from the anode.