Collision Theory in Chemical Kinetics – Complete Explanation
Collision Theory is a fundamental concept of Chemical Kinetics in Physical Chemistry. It explains how and why chemical reactions occur based on molecular collisions.
This topic is extremely important for Class 11, Class 12, NEET, JEE, and other competitive examinations.
Table of Contents
- Definition of Collision Theory
- Postulates of Collision Theory
- Effective Collision
- Activation Energy
- Factors Affecting Collision Theory
- Limitations
- MCQs
- FAQs
Definition of Collision Theory
According to Collision Theory, a chemical reaction occurs only when reactant molecules collide with:
- Sufficient kinetic energy (greater than or equal to activation energy)
- Proper orientation during collision
If either of these conditions is not fulfilled, the reaction does not occur even after collision.
Postulates of Collision Theory
1️⃣ Continuous Motion of Molecules
In gaseous reactions, molecules are in continuous random motion. Due to this motion, they collide frequently with each other.
2️⃣ Not All Collisions are Effective
Only those collisions that result in product formation are called effective collisions.
3️⃣ Activation Energy Requirement
For a reaction to occur, colliding molecules must possess energy equal to or greater than the activation energy.
Effective Collision
An effective collision is one in which:
- Molecules have sufficient energy
- Molecules collide with correct orientation
Only effective collisions lead to the formation of products and determine the rate of reaction.
Activation Energy in Collision Theory
Activation energy is the minimum energy required by reactant molecules to initiate a chemical reaction.
| Activation Energy | Reaction Rate |
|---|---|
| Low | Fast |
| High | Slow |
A lower activation energy increases the number of effective collisions.
Factors Affecting Collision Theory
Effect of Temperature
An increase in temperature increases the kinetic energy of molecules, resulting in more effective collisions and a higher reaction rate.
Effect of Catalyst
A catalyst increases the rate of reaction by lowering the activation energy without being consumed.
Related Topics: Chemical Kinetics | Rate of Reaction |
Limitations of Collision Theory
- Mainly applicable to gaseous reactions
- Fails to explain complex reactions accurately
- Does not quantitatively explain the orientation factor
Exam-Oriented MCQs
Q1. Collision Theory is most applicable to which phase?
A) Solid B) Liquid C) Gas D) Plasma
Q2. Which condition is essential for an effective collision?
A) Color B) Proper orientation C) Shape D) Volume
Frequently Asked Questions (FAQs)
Q. Which chapter includes Collision Theory?
Answer: Chemical Kinetics (Physical Chemistry)
Q. Is Collision Theory important for NEET and JEE?
Answer: Yes, it is a high-weightage topic for both NEET and JEE.
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