Question

Collision theory is satisfactory for:
A. First order reactions
B. Second order reactions
C. Bimolecular reactions
D. Zeroth order reactions

Answer 1

Hint: The collision theory helps in determining whether a reaction containing reactants will form a product. The formation is dependent on the manner of collision. If the collision is effective it will lead to the formation of a product.

Complete solution:
The collision theory helps to dictate whether a product will be formed or not in a reaction. If the orientation of the reactants is “proper” that is conducive for formation of compounds, then it is an effective collision and it will lead to the formation of a product. If the orientation is improper then it will not lead to formation of the product.
The theory states that in a group of reactions, products will be formed only in the reactions where effective collisions take place.
For a collision to be effective, it must follow certain conditions. The first condition is for the reacting molecules to have the right orientation before colliding.
The other condition is based on the energy of the colliding particles. All the reactant molecules are required to have a certain amount of energy. This energy is called activation energy. This energy can be defined as the extra potential energy that reactants are required to obtain so as to form a product.
The collisions can increase if the concentration of the substrate is increased. The addition of a catalyst also helps to increase the rate of the reaction because the activation energy is decreased and the effective collisions increase.
The collision theory is mostly used to obtain the rate of reaction for a bimolecular reaction. This is because it requires two or more reactants to undergo the required collision.
The first option that is first order reaction rate cannot be found because reactions which have only first order does not undergo physical collisions. This is the case with the fourth option as well that is, zeroth order. The second order reaction may or may not mean a bimolecular reaction as even reactions containing three reactants and be a second order reaction. For example, in some reactions the reactant which is taken in excess is considered to be zero order.
Whereas in bimolecular reactions, we are referring to reactions where there are only two reactants irrespective of whether they are in excess concentration or not.

Therefore, the answer to the question is option C that is, bimolecular reactions

Note: Bimolecular reactions only consist of two reacting molecules therefore the collisions are more predictable and a product is easily formed. Therefore, the collision theory is only applicable to bimolecular reactions.
It is also only applicable to elementary single step bimolecular reactions. The total energy of the two reactants must be in excess of the total activation energy of the reaction so that a product is formed.
A catalyst decreases the activation energy of the reaction.