As the temperature increases the number of effective collisions between reacting particles in a chemical reaction

A. initially increase, them decreases

B. Decreases

C. Initially decreases, then increase

D. Increases only

Answer: option A) initially increases, then decreases.

Justification:

The increase of the rate of effective collisions among particles as the temperature increases is explained by the collision theory in virtue of the increase of the kinetic energy.

This is, as the temperature increase so the kinetic energy increase and the higher the kinetic energy the greater the number of collisions and the greater the chances that this energy overcome the activation energy (the energy needed to start the reaction).

Now, as the reaction progress the number of reactants particles naturally decrease (some of them have been converted into product) so this lower number of particles means lower concentration which means lower collisions and, thereafter, a decrease in the reaction rate.