The process that you saw in Activity 14.7 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 an 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?
"

Given:

Activity 14.7 shows used for the purification of copper. 

To do:

To determine which electrode should be attached to the positive terminal of the battery and why.

Solution:

Let us observe the activity and components used for this arrangement:

1. A battery

2. Two connecting wires

3. Two copper plates connected to each terminal of the battery

5. A copper sulfate solution

Activity 14.7 shows the electrolysis process for the purification of impure copper. Now let us discuss which copper plate should be attached to the positive terminal of the battery:

Impure copper should be the positive electrode in electrolysis:

In electrolysis, the positive electrode$(anode)$ is made of impure copper and the pure copper acts as a negative electrode$(cathode)$. An impure copper rod should be attached to the positive terminal of the battery as the copper ions are positively charged and these positively charged copper ions are attracted by the copper plate which is attached to the negative terminal of the battery. In this type of arrangement, the copper ions from the impure rod get liberated into copper sulfate solution and the copper ions from the solution get deposited into the pure copper rod.