For an exothermic reaction

Options

A. `H_p` of the products is less than `H_r` of the reactants
B. `H_p` of the products is more than `H_r` of the reactants
C. `H_p` of the products is equal to `H_r` of the reactants
D. `triangleH` is always positive

Answer

### Step-by-Step Solution:

1. **Understanding Exothermic Reactions**:
- An exothermic reaction is one that releases heat to the surroundings. This means that the enthalpy change (ΔH) for the reaction is negative.

2. **Enthalpy Change Definition**:
- The enthalpy change (ΔH) is defined as:
\[ \Delta H = H_{\text{products}} - H_{\text{reactants}} \]
- For an exothermic reaction, since heat is released, the enthalpy of the products is less than that of the reactants. Therefore, ΔH will be negative.

3. **Analyzing the Options**:
- **Option 1**: Heat of the products is less than heat of the reactants.
- This statement is correct because it aligns with the definition of ΔH for exothermic reactions (ΔH < 0).
- **Option 2**: Heat of the products is more than heat of the reactants.
- This statement is incorrect because it contradicts the definition of exothermic reactions (ΔH < 0).
- **Option 3**: Heat of the products is equal to heat of the reactants.
- This statement is also incorrect because if the heat of products equals that of reactants, ΔH would be zero, indicating no reaction occurred.
- **Option 4**: ΔH is always positive.
- This statement is incorrect for exothermic reactions, as ΔH is negative.

4. **Conclusion**:
- The only correct statement regarding exothermic reactions is that the heat of the products is less than the heat of the reactants.

### Final Answer:
The correct condition for an exothermic reaction is that the heat of the products is less than the heat of the reactants.

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