Read the following and answer any four questions
During extraction of metals, electrolytic refining is used to obtain pure metals. During the process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. The solution of the metal salt is used as an electrolyte. On passing the current through the electrolyte, the pure metal from the anode dissolves from the electrolyte. An equivalent of pure metal from the electrolyte is deposited on the cathode.
Which of the metals are refined by electrolytic refining?
(i) Au (ii) Cu
(iii) Na (iv) K

Options

A. (i) and (ii)
B. (i) and (iii)
C. (ii) and (iii)
D. (ii) and (iv)

Explanation

To determine which metals can be refined by electrolytic refining, we need to analyze the options provided: Au (Gold), Cu (Copper), Na (Sodium), and K (Potassium).

### Step-by-Step Solution:

1. **Understanding Electrolytic Refining**:
- Electrolytic refining is a process used to purify metals. It involves using an electrolyte solution containing metal salts, where an impure metal acts as the anode and a pure metal strip acts as the cathode.

2. **Identifying the Metals**:
- The metals listed are:
- (i) Au (Gold)
- (ii) Cu (Copper)
- (iii) Na (Sodium)
- (iv) K (Potassium)

3. **Evaluating Each Metal**:
- **Au (Gold)**: Gold can be refined using electrolytic refining. It is often used in jewelry and electronics and is refined to achieve high purity.
- **Cu (Copper)**: Copper is commonly refined using electrolytic refining. This method is widely used in the industry to obtain pure copper for electrical wiring and other applications.
- **Na (Sodium)**: Sodium is not refined using electrolytic refining. It is typically produced through the electrolysis of molten sodium chloride (NaCl) and does not undergo refining in the same manner as metals like gold and copper.
- **K (Potassium)**: Similar to sodium, potassium is also not refined using electrolytic refining. It is produced through the electrolysis of potassium salts and does not require the refining process.

4. **Conclusion**:
- The metals that can be refined by electrolytic refining from the given options are:
- (i) Au (Gold)
- (ii) Cu (Copper)

### Final Answer:
The metals refined by electrolytic refining are **Au (Gold)** and **Cu (Copper)**.