In which of the following ways does an activated complex differ form an ordinary molecule?

Options

A. It is quite unstable and has no independent existence.
B. `Delta_(f)H^(ɵ)` is probably poistive.
C. The system has greater vibrational character.
D. The system has no vibrational character.

Answer

To determine how an activated complex differs from an ordinary molecule, we can analyze the characteristics of an activated complex and compare them to those of a regular molecule. Here’s a step-by-step breakdown of the differences:

### Step 1: Definition of Activated Complex
An activated complex, also known as a transition state, is a temporary arrangement of atoms that forms during a chemical reaction. It exists at the peak of the energy barrier that must be overcome for reactants to be converted into products.

**Hint:** Remember that an activated complex is not a stable entity; it is a fleeting state during a reaction.

### Step 2: Stability
Activated complexes are highly unstable and have a very short lifespan. They do not have an independent existence outside of the reaction process. In contrast, ordinary molecules are stable and can exist independently.

**Hint:** Consider the lifespan of the activated complex compared to ordinary molecules.

### Step 3: Energy Levels
Activated complexes possess higher energy compared to ordinary molecules. This high energy is necessary to overcome the activation energy barrier for the reaction to proceed. Ordinary molecules typically have lower energy levels.

**Hint:** Think about the energy required for a reaction to occur and how it relates to the stability of the molecules involved.

### Step 4: Vibrational Characteristics
Due to their high energy, activated complexes exhibit greater vibrational motion. This increased vibrational energy leads to more frequent and intense collisions between molecules, facilitating the reaction process. Ordinary molecules have less vibrational energy.

**Hint:** Reflect on how energy levels affect molecular motion and collision frequency.

### Conclusion
Based on the analysis, we can conclude that the activated complex differs from an ordinary molecule in the following ways:
1. **Instability**: Activated complexes are unstable and do not have an independent existence.
2. **Higher Energy**: They possess higher energy, resulting in a positive enthalpy change (ΔHf).
3. **Greater Vibrational Character**: They exhibit greater vibrational motion due to their high energy.

### Final Answer
The activated complex differs from an ordinary molecule in the following ways:
- It is unstable and has no independent existence (Option A).
- It has a higher energy level (Option B).
- It exhibits greater vibrational character (Option C).

Thus, the correct options are A, B, and C.