Bond energies are equal to dissociation energies in case of `:`

Options

A. monoatomic molecules
B. polyatomic molecules
C. diatomic molecules
D. all type of molecules

Explanation

To solve the question regarding when bond energies are equal to dissociation energies, we will analyze the options provided.

### Step-by-Step Solution:

1. **Understanding Bond Energy and Bond Dissociation Energy**:
- **Bond Energy**: This is the average energy required to break a bond in a molecule. It is typically calculated for all the bonds present in a molecule.
- **Bond Dissociation Energy**: This is the energy required to break a specific bond in a molecule. It is a more precise measurement for a particular bond.

2. **Analyzing the Options**:
- **Option A: Monoatomic Molecules**:
- Monoatomic molecules consist of single atoms (e.g., He, Ne). Since there are no bonds in monoatomic molecules, bond energy cannot be defined. Therefore, this option is incorrect.

- **Option B: Polyatomic Molecules**:
- Polyatomic molecules consist of more than two atoms (e.g., C6H12O6). These molecules have multiple types of bonds, and the bond energy is an average of all the different bonds present. Consequently, bond energy will not equal bond dissociation energy for specific bonds. Thus, this option is also incorrect.

- **Option C: All Diatomic Molecules**:
- Diatomic molecules consist of two atoms (e.g., H2, O2). In these cases, there is only one bond present. The energy required to break this bond (bond dissociation energy) is the same as the bond energy since there are no other bonds to average out. Therefore, this option is correct.

- **Option D: All Types of Molecules**:
- This option suggests that bond energy is equal to bond dissociation energy for all types of molecules, which is not true. As established, this is only true for diatomic molecules. Thus, this option is incorrect.

3. **Conclusion**:
- The correct answer is **Option C: All Diatomic Molecules**. In diatomic molecules, bond energy is equal to bond dissociation energy because there is only one bond to consider.

### Final Answer:
Bond energies are equal to dissociation energies in the case of **All Diatomic Molecules**.

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