Assertion `(A)`: Temporary hardness in water is due to the presence of chlorides of magnesium.
Reason `(R)` :Temporary hardness is removed by Clark's method.

Explanation

To solve the assertion and reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Analyze the Assertion (A)
The assertion states: "Temporary hardness in water is due to the presence of chlorides of magnesium."

- **Explanation**: Temporary hardness in water is primarily caused by the presence of bicarbonates and carbonates of calcium and magnesium. Chlorides of magnesium do not contribute to temporary hardness. Therefore, this assertion is **false**.

### Step 2: Analyze the Reason (R)
The reason states: "Temporary hardness is removed by Clarke's method."

- **Explanation**: Clarke's method, also known as lime softening, involves adding calcium hydroxide (lime) to water. This process helps to precipitate out the bicarbonates and carbonates, effectively removing temporary hardness. Therefore, this reason is **true**.

### Conclusion
Based on the analysis:
- Assertion (A) is **false**.
- Reason (R) is **true**.

Thus, the correct conclusion is that the assertion is false while the reason is true.

### Final Answer
- Assertion (A) is false.
- Reason (R) is true.