Which graph shows zero activation energy ?

Options

A.
B.
C.
D.

Answer

To determine which graph shows zero activation energy, we need to understand the concept of activation energy and how it is represented graphically.

### Step-by-Step Solution:

1. **Understand Activation Energy**:
Activation energy (Ea) is the minimum energy required for a chemical reaction to occur. It is represented as the energy difference between the reactants and the transition state.

2. **Graph Representation**:
In a typical energy versus reaction progress graph:
- The x-axis represents the reaction progress.
- The y-axis represents the energy of the system.
- The reactants are at a certain energy level, and the transition state is at a higher energy level, creating an energy barrier (activation energy).

3. **Identify Characteristics of Zero Activation Energy**:
- For a reaction to have zero activation energy, there should be no energy barrier between the reactants and the transition state.
- This means that the energy level of the reactants and the transition state must be the same.

4. **Analyze the Given Graph Options**:
- **Option 1**: Shows a clear energy difference between reactants and transition state, indicating activation energy.
- **Option 2**: Similar to Option 1, shows an energy barrier.
- **Option 3**: Shows the reactants and transition state at the same energy level, indicating that the reaction can occur spontaneously without any energy input. This represents zero activation energy.
- **Option 4**: Similar to Options 1 and 2, shows an energy barrier.

5. **Conclusion**:
Based on the analysis, **Option 3** is the graph that shows zero activation energy because it indicates that the reactants and transition state are at the same energy level, allowing the reaction to proceed spontaneously.

### Final Answer:
The graph that shows zero activation energy is **Option 3**.