The enthalpy of reaction, `Delta_(1) H`, is

Options

A. `Delta_(r) = H` (product) `+ H` (reactants)
B. `Delta_(r) = H` (reactants) `- H` (products)
C. `Delta_(r) =H` (product) `- H` (reactants)
D. `Delta_(r) = H` (reactants) `+ H` (products)

Explanation

To solve the question regarding the enthalpy of reaction, ΔH, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Enthalpy (ΔH)**:
- Enthalpy (H) is a measure of the total energy of a thermodynamic system. The change in enthalpy (ΔH) during a reaction indicates whether the reaction absorbs or releases heat.

2. **Identify the Reaction**:
- Consider a general reaction:
\[ A + B \rightarrow C + D \]
- Here, A and B are reactants, while C and D are products.

3. **Define ΔH**:
- The enthalpy change for the reaction can be expressed as:
\[ ΔH = H_{\text{products}} - H_{\text{reactants}} \]
- This means we subtract the total enthalpy of the reactants from the total enthalpy of the products.

4. **Determine the Sign of ΔH**:
- If the enthalpy of the products (H_products) is greater than that of the reactants (H_reactants), then ΔH will be positive, indicating that the reaction is endothermic (absorbs heat).
- Conversely, if H_products is less than H_reactants, ΔH will be negative, indicating that the reaction is exothermic (releases heat).

5. **Conclusion**:
- The enthalpy of reaction, ΔH, can be calculated using the formula:
\[ ΔH = H_{\text{C}} + H_{\text{D}} - (H_{\text{A}} + H_{\text{B}}) \]
- Depending on the values of H for the reactants and products, ΔH can be positive or negative.