Activation energy is:

Options

A. The amount of energy to be added to the actual energy of a molecule so that the threshold energy is reached
B. The amount of energy the molecule must contain so that it reacts
C. The energy which a molecule should have in order to enter into an effective collision
D. The average kinetic energy of the molecule

Answer

**Step-by-Step Text Solution:**

1. **Definition of Activation Energy**: Activation energy (Ea) is defined as the minimum amount of energy that must be provided to reactants in a chemical reaction for the reaction to occur. It is the energy barrier that must be overcome for reactants to be transformed into products.

2. **Energy Requirement for Reactions**: In a chemical reaction, molecules must collide with sufficient energy and proper orientation to break bonds in the reactants and form new bonds in the products. The energy required to initiate this process is known as activation energy.

3. **Graphical Representation**: To visualize activation energy, we can use a potential energy diagram. In this diagram:
- The x-axis represents the reaction coordinate (progress of the reaction).
- The y-axis represents potential energy.
- The reactants start at a certain energy level, and as the reaction progresses, they reach a peak (the transition state) before forming products at a lower energy level.

4. **Transition State**: The peak of the graph represents the transition state, which is an unstable state where the reactants are in the process of being converted into products. The energy difference between the reactants and the transition state is the activation energy.

5. **Kinetic Energy and Effective Collisions**: For a reaction to occur, the reactant molecules must have enough kinetic energy to collide effectively. This means that they must overcome the repulsive forces caused by their electrons. The activation energy ensures that only those molecules with sufficient energy can successfully collide and react.

6. **Conclusion**: Therefore, activation energy is a crucial concept in chemical kinetics as it determines the rate at which a reaction will proceed. A higher activation energy means that fewer molecules will have the required energy to react, resulting in a slower reaction rate.

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