The standard enthalpy of formation of which of the following is zero

Options

A. `CH_(3)OH`
B. HF
C. `H_(2)O`
D. `F_(2)`

Explanation

To determine the standard enthalpy of formation (ΔH_f°) of the given substances, we need to understand what standard enthalpy of formation means. It is defined as the change in enthalpy when one mole of a compound is formed from its elements in their standard states. The standard enthalpy of formation for any element in its standard state is defined to be zero.

### Step-by-Step Solution:

1. **Understand Standard Enthalpy of Formation**:
- The standard enthalpy of formation (ΔH_f°) is the heat change that results when one mole of a compound is formed from its elements in their standard states.

2. **Identify the Elements and Their Standard States**:
- Elements in their standard states have a ΔH_f° of zero. For example, O2(g), N2(g), and F2(g) are all elements in their standard states.

3. **Analyze the Given Options**:
- Check each option to see if it is an element in its standard state:
- **Option 1**: Substance A (not specified)
- **Option 2**: Substance B (not specified)
- **Option 3**: Substance C (not specified)
- **Option 4**: F2 (Fluorine gas)

4. **Determine the Standard Enthalpy of Formation for F2**:
- F2 is a diatomic molecule formed from fluorine atoms, which are elements in their standard state. Therefore, the standard enthalpy of formation for F2 is zero.

5. **Conclusion**:
- The standard enthalpy of formation of F2 is zero because it is an element in its standard state.

### Final Answer:
The standard enthalpy of formation of F2 is zero.

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