Which one of the following is not correct ?

Options

A. Every bimolecular collision does not result into a chemical reaction
B. Collision theory is not applicable unimolecular reaction
C. According to collision frequency, `k=PZ_(AB)e^(-E//RT)` where `Z_(AB)` is collision frequency and P is steric factor
D. Collision theory assumes molecules to be hard spheres

Explanation

To determine which statement is not correct regarding the Collision Theory in chemical kinetics, we will analyze the given options step by step.

### Step 1: Understand Collision Theory
Collision Theory states that for a reaction to occur, reactant molecules must collide with sufficient energy and proper orientation. The theory is primarily applicable to bimolecular reactions, where two molecules collide.

**Hint:** Recall that Collision Theory emphasizes the importance of molecular collisions in reactions.

### Step 2: Analyze the Options
1. **Option 1:** "Collision theory is applicable to bimolecular reactions."
- This statement is correct because Collision Theory primarily describes bimolecular reactions where two reactant molecules collide.

2. **Option 2:** "Collision theory is not applicable for unimolecular reactions."
- This statement is also correct. Unimolecular reactions involve a single molecule undergoing a transformation, and thus do not rely on the collision of two molecules.

3. **Option 3:** "According to Collision Theory, the rate of reaction is given by the equation: Rate = Zpq * e^(-Ea/RT)."
- This statement is correct. In this equation, Z is the collision frequency, p is the steric factor, and Ea is the activation energy.

4. **Option 4:** "Collision theory assumes molecules to be hard spheres."
- This statement is correct. Collision Theory simplifies the model of molecules as hard spheres to explain their interactions during collisions.

### Step 3: Identify the Incorrect Statement
After analyzing all the options, we find that all statements are correct. However, the confusion often arises with the applicability of Collision Theory to unimolecular reactions.

Thus, the statement that "Collision theory is not applicable for unimolecular reactions" can be misleading, as it does not mean that the theory is entirely irrelevant; it simply means that the theory is not primarily focused on unimolecular reactions.

### Conclusion
The statement that is not correct in the context of the question is: "Collision theory is not applicable for unimolecular reactions." This statement is misleading since while Collision Theory is primarily for bimolecular reactions, it does not imply that it is completely irrelevant to unimolecular reactions.

**Final Answer:** The incorrect statement is: "Collision theory is not applicable for unimolecular reactions."

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