The process that you saw in Activity 11.7 is used for the 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 the battery and why?

The thick rod of impure copper should be attached to the positive terminal of the battery in the purification process of copper. This is because, during the passage of electric current through copper sulphate solution, it breaks down into copper and sulphate ions. The positively charged copper ions are attracted to the negative terminal of the battery, where they get deposited on the thin plate of pure copper. Simultaneously, the impure copper rod, linked to the positive terminal, contributes copper ions to compensate for the loss in the solution. This ensures the overall purification of copper during the process.