The Activation energy for a chemical reaction mainly depends upon

Options

A. the difference in energies of reactants and products
B. the sum of energies of reactants and products
C. the difference in energy of intermediate complex with the average energy of reactantsand products
D. the difference in energy of intermediate complex and the average energy of reactants.

Answer

To determine what the activation energy for a chemical reaction mainly depends upon, we can analyze the options provided and the underlying concepts of chemical kinetics.

### Step-by-Step Solution:

1. **Understanding Activation Energy**:
- Activation energy (Ea) is the minimum energy required for a chemical reaction to occur. It is the energy barrier that must be overcome for reactants to be transformed into products.

2. **Energy Diagram**:
- To visualize activation energy, we can draw an energy profile diagram. In this diagram, the y-axis represents energy, while the x-axis represents the progress of the reaction.
- The reactants start at a certain energy level, and as the reaction progresses, they reach a peak known as the transition state or intermediate complex before falling to the energy level of the products.

3. **Identifying Key Energies**:
- The activation energy is the difference in energy between the reactants and the transition state (intermediate complex).
- If the reaction is exothermic, the energy of the products will be lower than that of the reactants, resulting in a negative change in enthalpy (ΔH).

4. **Analyzing the Options**:
- **Option 1**: The difference in energies of reactants and products.
- This is not correct, as activation energy does not depend on the energy difference between reactants and products.
- **Option 2**: The sum of energies of reactants and products.
- This is also incorrect; activation energy is not based on the sum of energies.
- **Option 3**: The difference in energy of the intermediate complex with the activation energy of reactants and products.
- This option is misleading and does not accurately describe the dependence of activation energy.
- **Option 4**: The difference in energy of the intermediate complex and the average energy of the reactants.
- This is the correct option, as activation energy is defined as the energy required to reach the transition state from the reactants.

5. **Conclusion**:
- Therefore, the activation energy for a chemical reaction mainly depends upon the difference in energy of the intermediate complex and the average energy of the reactants.

### Final Answer:
**The activation energy for a chemical reaction mainly depends upon the difference in energy of the intermediate complex and the average energy of the reactants. (Option 4)**

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