Which of the following molecules will have different values of standard molar enthalpy of formation, one calculated using bond energies and other calculated calorimetrically?

Options

A. `C_2H_6 (g)`
B. `1, 3` - butadiene
C. 1, 3 -cyclohexadiene
D. `N_2O`

Explanation

To determine which molecules have different values of standard molar enthalpy of formation when calculated using bond energies versus calorimetrically, we need to analyze the presence of resonance in the given molecules. Resonance can lead to extra stability that is not accounted for in theoretical calculations based on bond energies.

### Step-by-Step Solution:

1. **Understanding Standard Molar Enthalpy of Formation**:
- The standard molar enthalpy of formation is the change in enthalpy when one mole of a compound is formed from its elements in their standard states.
- It can be calculated using bond energies (theoretical approach) or determined experimentally (calorimetrically).

2. **Identifying the Molecules**:
- The question provides several molecules, including C2H6 (ethane), 1,3-butadiene, 1,3-cyclohexadiene, and N2O.
- We need to identify which of these molecules have resonance structures.

3. **Analyzing Each Molecule**:
- **C2H6 (Ethane)**: This molecule does not have resonance. Its theoretical and experimental values should match.
- **1,3-butadiene**: This molecule has resonance due to the alternating double bonds. The resonance provides extra stability, leading to a difference between the theoretical and experimental values.
- **1,3-cyclohexadiene**: Similar to 1,3-butadiene, this molecule also has resonance, which will cause a difference in the calculated values.
- **N2O**: This molecule does not exhibit resonance in a way that would affect the enthalpy calculations significantly.

4. **Conclusion**:
- The molecules that will have different values of standard molar enthalpy of formation calculated using bond energies and calorimetrically are **1,3-butadiene** and **1,3-cyclohexadiene** due to their resonance structures providing extra stability.

### Final Answer:
The answer is **1,3-butadiene (option 2) and 1,3-cyclohexadiene (option 3)**.