Question

For purification of copper, a thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from the impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of battery?

• A. Pure copper
• B. Copper
• C. Impure copper
• D. Aluminun

Answer 1

The correct option is C Impure copper

Copper ion is positively charged. It is attracted towards the plate which is connected to the negative terminal of the battery. As copper ions are transferred to the thin copper plate, this thin pure copper plate must be connected to the negative terminal of the battery. Consequently, impure copper rod is connected to the positive terminal of the battery (Refer fig. given below), Reactions that take place in this process are:
(i) At cathode (negative copper plate):
${Cu}^{2+}+2e\to Cu$ (Reduction of Cu)
The Cu atoms so produced get deposited on the cathode.
(ii) At anode (positive copper plate)
$Cu\to {Cu}^{2+}+2e^{-}$ (oxidation of Cu)