in the purification of copper,which electrode should be connected to the positive terminal of the battery and why?
In the purification of copper, the positive terminal of the battery should be connected to the copper impure electrode, also known as the anode. This is because during the purification process, oxidation occurs at the anode.
To understand why the anode is connected to the positive terminal, we need to explore the process of electrolysis.
Electrolysis involves passing an electric current through a solution or molten compound, in this case, a copper sulfate solution, to decompose it into its constituent elements. In the purification of copper, the impure copper serves as the anode, while a pure copper electrode serves as the cathode.
The copper sulfate solution contains copper ions (Cu2+) and sulfate ions (SO4^2-). When an electric current is passed through the solution, the positive copper ions (Cu2+) are attracted to the negative cathode, where they gain electrons and are reduced, forming pure copper metal. This process allows the impurities in the copper to be removed, resulting in purified copper.
At the same time, on the anode side, the copper atoms from the impure copper electrode lose electrons, oxidizing into copper ions (Cu2+). These copper ions go into the solution. The impurities and interactions from the anode collect at the bottom of the electrolysis setup as anode mud or sludge.
Now, coming back to the initial question, when the positive terminal of the battery is connected to the anode, it provides a flow of electrons from the anode to the cathode through the external circuit. This electron flow helps in the oxidation of copper from the impure electrode (anode) into the copper ions (Cu2+), which then dissolve into the solution.
In summary, to promote the oxidation process and facilitate the purification of copper, the positive terminal of the battery should be connected to the copper impure electrode (anode).