A: `Delta H` is positive for endothermic reactions.
R : If total enthalpies of reactants and products are `H_(R) & H_(P)` respectively then for an endothermic reaction `H_(R) lt H_(P)`

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 is true statement but Reason is false, then mark (3)

Answer

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

### Assertion (A):
- **Delta H is positive for endothermic reactions.**

### Reason (R):
- **If total enthalpies of reactants and products are \( H_R \) and \( H_P \) respectively, then for an endothermic reaction \( H_R < H_P \).**

### Step-by-Step Solution:

1. **Understanding Endothermic Reactions:**
- In an endothermic reaction, energy is absorbed from the surroundings. This means that the products of the reaction have a higher energy content than the reactants.

2. **Defining Delta H:**
- The change in enthalpy (\( \Delta H \)) for a reaction can be defined as:
\[ \Delta H = H_P - H_R \]
- Where \( H_P \) is the enthalpy of the products and \( H_R \) is the enthalpy of the reactants.

3. **Analyzing the Sign of Delta H:**
- For endothermic reactions, since energy is absorbed, the enthalpy of the products is greater than that of the reactants. Thus:
\[ H_P > H_R \]
- This implies that:
\[ \Delta H = H_P - H_R > 0 \]
- Therefore, \( \Delta H \) is positive for endothermic reactions.

4. **Relating the Reason to the Assertion:**
- The reason states that for an endothermic reaction, \( H_R < H_P \). This is consistent with our previous conclusion that \( H_P \) is greater than \( H_R \) for endothermic reactions.
- Hence, the reason correctly explains the assertion.

5. **Conclusion:**
- Both the assertion and the reason are true, and the reason provides a correct explanation for the assertion.

### Final Answer:
- Both A and R are true, and R is the correct explanation of A.

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