`H(g) + O(g) rightarrow O - H(g), Delta H` for this reaction is

Options

A. Heat of formation of O - H
B. Bond energy of O - H
C. Heat of combustion of `H_(2)`
D. Zero at all temperatures

Answer

To determine the enthalpy change (ΔH) for the reaction:

\[ \text{H(g)} + \text{O(g)} \rightarrow \text{O-H(g)} \]

we can analyze the options provided and understand the thermodynamic principles involved.

### Step-by-Step Solution:

1. **Identify the Reaction**:
The reaction involves hydrogen gas (H) and oxygen gas (O) combining to form a hydroxyl radical (O-H).

2. **Understanding Enthalpy Change (ΔH)**:
ΔH represents the change in enthalpy during a chemical reaction. It can be related to the bond energies of the reactants and products.

3. **Bond Formation**:
In this reaction, a bond is formed between hydrogen and oxygen to create the O-H bond. The formation of a bond typically releases energy, which means ΔH will be negative.

4. **Options Analysis**:
- **Option A**: Heat of formation of OH - This is relevant because the formation of O-H from its elements (H and O) is indeed related to the enthalpy change of the reaction.
- **Option B**: Bond energy of O-H - This is also relevant as it represents the energy associated with the O-H bond formation.
- **Option C**: Heat of combustion of H2 - This is not directly relevant to the formation of O-H from H and O.
- **Option D**: Zero at all temperatures - This is incorrect as the formation of a bond involves energy changes.

5. **Conclusion**:
The most appropriate answer is **Option B**: Bond energy of O-H, as it directly relates to the energy change associated with the formation of the O-H bond.

### Final Answer:
The ΔH for the reaction is related to the bond energy of O-H, thus the answer is **Option B**.

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