Q.12 The process that you saw in Activity 14.7 is used for purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from 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?

Copper ions are positively charged ions. So the copper ions will be attracted towards the plate which is connected to the negative terminal of the battery.

As copper ions from the thick impure copper rode must be transferred to the thin pure copper plate, so the thin pure copper plate must be connected to the negative terminal of the battery.

Consequently, the impure copper rod will be connected to the positive terminal of the battery so that the positive copper ions from the impure copper rod will transfer to the negative terminal of the thin pure copper plate.