A: Solubility of NaCl increases with temperature.
R: Dissolution of NaCl is an endothermic process.

Options

A. It both assertion & Reason are true and the reason is the correct explanation of the assertion, the mark (1)
B. If both assertion & Reason are true but the reason is not the correct explanation of the assertion then mark (2)
C. IF Assertion is true statement but Reason is false then mark (3)
D. IF both Assertion and Reason are false statements, then mark (4)

Answer

To solve the assertion-reason question regarding the solubility of NaCl and its dissolution process, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "the solubility of NaCl increases with temperature."
- This means that as the temperature of the solution increases, more NaCl can dissolve in it.

2. **Understanding the Reason**:
- The reason states that "the dissolution of NaCl is an endothermic process."
- An endothermic process is one that absorbs heat from the surroundings.

3. **Analyzing the Dissolution of NaCl**:
- When NaCl dissolves in water, it dissociates into its constituent ions: Na⁺ and Cl⁻.
- This process requires energy to break the ionic bonds in NaCl and to separate the ions, which is why it is classified as endothermic.

4. **Relating Temperature and Solubility**:
- For endothermic reactions, according to Le Chatelier's principle, increasing the temperature shifts the equilibrium to favor the formation of products (in this case, the dissolved ions).
- Therefore, as the temperature increases, the solubility of NaCl also increases because more NaCl can dissolve in the solution.

5. **Conclusion**:
- Both the assertion and the reason are correct.
- The reason provided is a correct explanation for the assertion.

### Final Answer:
- The assertion "the solubility of NaCl increases with temperature" is true.
- The reason "the dissolution of NaCl is an endothermic process" is also true and correctly explains the assertion.