Which of the following metals can be purified by electrolytic refining?

1. Cu, and Zn     

2. Ge, and Si     

3. Zr, and Ti     

4. Zn, and Hg

HINT: Cu and Zn are purified by electrolytic refining.
Explanation:
STEP 1:
Electrolytic refining is the process of refining a metal (mainly copper) by the process of electrolysis.
The clean or pure metal is formed at the cathode when the electrical current of a sufficient voltage is applied
by dissolving impure metal at the anode.
Copper and zinc are two metals that are generally purified by using electrolyte refining.
In this process, impure metal is used as an anode and pure metal is used as a cathode.
STEP 2:
Impurities from the blister copper or impure zinc deposit as anode mud.
The reactions involved are: 
At anode: Cu(Impure) Cu+2  + 2e-At cathode : Cu+2  Cu(Pure) +2e-