To determine which statements about resonance are true, we will analyze each option one by one based on the principles of resonance in chemistry.
### Step-by-Step Solution:
1. **Option (a): Resonance is an intramolecular process.**
- **Analysis**: Resonance occurs within a single molecule, where electrons are delocalized across different bonds or atoms. Therefore, this statement is true.
- **Conclusion**: True.
2. **Option (b): Resonance involves delocalization of both sigma and pi electrons.**
- **Analysis**: Resonance primarily involves the delocalization of pi electrons and lone pairs, not sigma electrons. Sigma bonds are localized and do not participate in resonance. Therefore, this statement is false.
- **Conclusion**: False.
3. **Option (c): Resonance involves delocalization of pi electrons and lone pairs only.**
- **Analysis**: This statement accurately describes resonance, as it involves the delocalization of pi electrons and lone pairs. Therefore, this statement is true.
- **Conclusion**: True.
4. **Option (d): Resonance decreases potential energy of a molecule.**
- **Analysis**: Resonance stabilizes a molecule by lowering its potential energy due to the delocalization of electrons. Therefore, this statement is true.
- **Conclusion**: True.
5. **Option (e): Resonance has no effect on the potential energy of a molecule.**
- **Analysis**: This statement contradicts the previous analysis. Resonance does affect potential energy by decreasing it. Therefore, this statement is false.
- **Conclusion**: False.
6. **Option (f): Resonance is the only way to increase molecular stability.**
- **Analysis**: While resonance increases stability, there are other factors (like hyperconjugation and inductive effects) that also contribute to molecular stability. Therefore, this statement is false.
- **Conclusion**: False.
7. **Option (g): Resonance is not the only way to increase molecular stability.**
- **Analysis**: This statement is true as discussed in the previous point. Other factors can also stabilize a molecule. Therefore, this statement is true.
- **Conclusion**: True.
8. **Option (h): Any resonating molecule is always more stable than any non-resonating molecule.**
- **Analysis**: This statement is false because stability can depend on other factors, and not all resonating structures are more stable than non-resonating ones. For example, a non-polar molecule can be more stable than a polar resonating molecule.
- **Conclusion**: False.
9. **Option (i): The canonical structure explains all features of a molecule.**
- **Analysis**: Canonical structures (or resonance forms) do not provide a complete picture of the actual molecule; they are just hypothetical representations. Therefore, this statement is false.
- **Conclusion**: False.
10. **Option (j): The resonance hybrid explains all features of a molecule.**
- **Analysis**: The resonance hybrid is a better representation of the actual molecule as it accounts for the delocalization of electrons. Therefore, this statement is true.
- **Conclusion**: True.
11. **Option (k): Resonating structures are real and resonance hybrid is imaginary.**
- **Analysis**: This statement is incorrect because the resonance hybrid represents the actual distribution of electrons, while the individual resonance structures are hypothetical. Therefore, this statement is false.
- **Conclusion**: False.
12. **Option (l): Resonance hybrid is real and resonating structures are imaginary.**
- **Analysis**: This statement is true as the resonance hybrid reflects the actual electron distribution in the molecule, while the canonical structures are merely theoretical. Therefore, this statement is true.
- **Conclusion**: True.
13. **Option (m): Resonance hybrid is always more stable than all canonical structures.**
- **Analysis**: The resonance hybrid is indeed more stable than any individual canonical structure because it represents the average of all possible structures, thus reflecting the true electron delocalization. Therefore, this statement is true.
- **Conclusion**: True.
### Summary of True Statements:
- True: (a), (c), (d), (g), (j), (l), (m)
- False: (b), (e), (f), (h), (i), (k)
