The collision theory explains reaction rates in terms of

Analysis

The question asks for the fundamental basis of the collision theory in chemical kinetics. This theory is used to explain how chemical reactions occur and why reaction rates differ under various conditions.

Concept Explanation

The collision theory states that for a chemical reaction to occur between reactant particles, three conditions must be met:

1. Collision: The reactant particles must collide with each other.
2. Orientation: The particles must collide with the correct spatial orientation.
3. Activation Energy: The particles must collide with sufficient kinetic energy (at least equal to the activation energy) to break existing bonds and form new ones.

The rate of reaction is directly proportional to the number of effective collisions occurring per unit time. Therefore, the more frequently reactant particles collide with the necessary energy and orientation, the faster the reaction proceeds.

Step-by-Step Solution

1. Analyze the reactants vs. products: Collision theory focuses on the interaction between reactants. Products are the result of the reaction, so their collision frequency does not determine the rate of the forward reaction. This eliminates options A and D.
2. Evaluate the role of size: While the size of particles can influence how often they collide (steric factor), the theory is primarily defined by the frequency and energy of the collisions of the reactants, not just their physical size. This makes option C less accurate than B.
3. Focus on frequency: The core principle is that the rate of reaction is dependent on the frequency of effective collisions between reactant molecules. As the frequency of these collisions increases (e.g., by increasing concentration, pressure, or temperature), the reaction rate increases.

Conclusion

The collision theory explains that the rate of a reaction is determined by how often the reactant particles collide with enough energy to react. Thus, it is defined by the frequency of collision of the reactants.

Exam Tip: Whenever you see a question about "Collision Theory," always look for keywords like "effective collisions," "activation energy," and "frequency of collisions." Remember: No collision, no reaction!