A: All reactions which are exothermic are spontaneous
R: All reactions in which entropy increases are spontaneous

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark (1)
B. If both Assertion & Reason are true and 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 is false, then mark (3)

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided in the question.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "All reactions which are exothermic are spontaneous."
- An exothermic reaction is one where the change in enthalpy (ΔH) is negative (ΔH < 0).
- However, spontaneity of a reaction is determined by the Gibbs free energy change (ΔG), which is given by the equation:
\[ \Delta G = \Delta H - T \Delta S \]
- For a reaction to be spontaneous, ΔG must be negative (ΔG < 0).

2. **Analyzing the Assertion**:
- While exothermic reactions have ΔH < 0, they can still be non-spontaneous if the entropy change (ΔS) is negative and large enough to make ΔG positive.
- Therefore, the assertion is **false** because not all exothermic reactions are spontaneous.

3. **Understanding the Reason (R)**:
- The reason states that "All reactions in which entropy increases are spontaneous."
- An increase in entropy (ΔS > 0) suggests that the disorder of the system is increasing.
- However, just having an increase in entropy does not guarantee spontaneity. We must also consider the enthalpy change (ΔH).

4. **Analyzing the Reason**:
- For a reaction to be spontaneous, we need ΔG to be negative. If ΔH is positive (endothermic) and ΔS is also positive, the reaction can still be non-spontaneous at low temperatures because ΔG could be positive.
- Therefore, the reason is also **false** because it does not account for the enthalpy change.

5. **Conclusion**:
- Both the assertion and the reason are false.
- Thus, the correct answer is that both A and R are false.

### Final Answer:
Both assertion and reason are false.