According to the collision theory of reaction rates, an increase in the temperature at which the reaction occurs will, in turn, increase the rate of the reaction. This is caused due to:

Greater number of molecules are having the activation energy (threshold energy)

The correct answer is option 1. Greater number of molecules are having the activation energy (threshold energy).

Let us delve into the explanation of why increasing temperature increases the rate of a reaction according to collision theory:

The collision theory of reaction rates states that for a chemical reaction to occur, reactant molecules must collide with sufficient energy (activation energy, \( E_a \)) and proper orientation.

Effect of Temperature:

Temperature is a measure of the average kinetic energy of molecules in a system.

When temperature increases:

The kinetic energy of molecules increases. Molecules move faster and collide more frequently. Collisions between molecules occur with greater force.

Impact on Reaction Rate:

Increasing temperature affects reaction rate through several mechanisms:

Higher Energy Collisions: At higher temperatures, more molecules have kinetic energies equal to or greater than the activation energy (\( E_a \)).

Increased Collision Frequency: Faster-moving molecules collide more frequently.

Effective Collisions: A greater proportion of collisions occur with sufficient energy and proper orientation to lead to a chemical reaction.

Specific Explanation:

Greater number of molecules are having the activation energy (threshold energy):

As temperature increases, the distribution of kinetic energies among molecules shifts to higher values. According to the Boltzmann distribution, more molecules will have energies equal to or greater than \( E_a \). Therefore, increasing temperature means a greater number of molecules are capable of overcoming the activation energy barrier when they collide, thereby increasing the reaction rate.

Conclusion: In summary, the increase in reaction rate with temperature is primarily due to a greater number of molecules possessing kinetic energies sufficient to meet or exceed the activation energy required for the reaction. This aligns with the collision theory's principle that effective collisions between reactant molecules are necessary for a chemical reaction to proceed.