In the reaction,
`CO_(2)(g)+H_(2)(g)toCO(g)+H_(2)O(g)," "DeltaH=2.8 kJ`
`DeltaH` represents :

Options

A. Heat of formation
B. Heat of combustion
C. Heat of neutralization
D. Heat of reaction

Answer

To determine what ΔH represents in the reaction \( CO_2(g) + H_2(g) \rightarrow CO(g) + H_2O(g) \) with ΔH = 2.8 kJ, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding ΔH**:
- ΔH represents the change in enthalpy during a chemical reaction. It indicates whether the reaction absorbs or releases heat.

2. **Analyzing the Reaction**:
- The given reaction involves the conversion of carbon dioxide and hydrogen gas into carbon monoxide and water vapor.

3. **Evaluating the Options**:
- **Option 1: Heat of Formation**:
- The heat of formation is the energy change when one mole of a compound is formed from its elements in their standard states. In this reaction, \( CO_2 \) is not in its elemental state (it is a compound), so this option is incorrect.

- **Option 2: Heat of Combustion**:
- The heat of combustion is the energy released when a substance is burned in the presence of oxygen. Since there is no combustion occurring in this reaction (no oxygen is involved), this option is also incorrect.

- **Option 3: Heat of Neutralization**:
- The heat of neutralization refers to the heat change when an acid reacts with a base to form water and a salt. There is no acid-base reaction in this case, making this option incorrect as well.

- **Option 4: Heat of Reaction**:
- The heat of reaction is the heat absorbed or released during a chemical reaction. Since ΔH is given as +2.8 kJ, it indicates that the reaction absorbs heat (endothermic reaction). Therefore, this option is correct.

4. **Conclusion**:
- Based on the analysis, ΔH in this reaction represents the heat of reaction, which is the heat absorbed during the reaction.

### Final Answer:
ΔH represents the heat of reaction.

---