Assertion `(A):` A saturated solution of `KCl` is used in making salt bridge.
Reason `(R):` Ionic mobilities of `K^(+)` and `Cl^(-)` are comparable.

Options

A. If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`.
B. If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`.
C. If `(A)` is correct, but `(R)` is incorrect.
D. If `(A)` is incorrect, `(R)` is correct.

Explanation

To solve the question regarding the assertion and reason about the use of a saturated solution of KCl in making a salt bridge, we can break it down into a step-by-step analysis.

### Step 1: Understand the Assertion
- The assertion states that "A saturated solution of KCl is used in making salt bridge."
- A salt bridge is an essential component in electrochemical cells that allows the flow of ions and maintains electrical neutrality.

**Hint:** Recall the purpose of a salt bridge in electrochemical cells.

### Step 2: Understand the Reason
- The reason states that "Ionic mobilities of K⁺ and Cl⁻ are comparable."
- Ionic mobility refers to the speed at which an ion moves through a medium under the influence of an electric field. Comparable ionic mobilities ensure that both ions can migrate to their respective electrodes at similar rates.

**Hint:** Think about what happens if one ion moves faster than the other in maintaining neutrality.

### Step 3: Analyze the Functions of a Salt Bridge
- A salt bridge serves two main functions:
1. It completes the circuit by allowing the flow of ions.
2. It maintains electrical neutrality in the electrochemical cell.

**Hint:** Consider how the flow of ions affects the charges at the electrodes.

### Step 4: Evaluate the Assertion
- Since KCl dissociates into K⁺ and Cl⁻ ions in solution, it can effectively facilitate the movement of ions needed to complete the circuit and maintain neutrality.
- Therefore, the assertion is **true**.

**Hint:** Look at the properties of KCl in solution and its role in electrochemistry.

### Step 5: Evaluate the Reason
- For the salt bridge to function effectively, the ionic mobilities of K⁺ and Cl⁻ must be comparable. If one ion moves significantly faster than the other, it could lead to an imbalance in charge, disrupting neutrality.
- Since K⁺ and Cl⁻ have comparable ionic mobilities, the reason is also **true**.

**Hint:** Reflect on the implications of unequal ionic mobilities in a salt bridge.

### Step 6: Conclusion
- Both the assertion (A) and reason (R) are correct, and the reason provides a valid explanation for the assertion. Therefore, the correct answer is that both A and R are correct, and R is the correct explanation of A.

**Final Answer:** Both A and R are correct, and R is the correct explanation of A.