In collision theory of chemical reaction, `Z_(AB)` represents

Options

A. the fraction of molecules with energies greater than `E_a`
B. the collision frequency of reactants, A and B
C. steric factor
D. the fraction of molecules with energies equal to `E_a`

Answer

To solve the question regarding what `Z_(AB)` represents in the collision theory of chemical reactions, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Collision Theory**:
- Collision theory states that for a chemical reaction to occur, reactant particles must collide with each other. However, not all collisions result in a reaction.

2. **Defining Key Terms**:
- **Activation Energy (Ea)**: This is the minimum energy required for a reaction to occur. Only collisions with energy equal to or greater than Ea can lead to a reaction.
- **Collision Frequency (ZAB)**: This term specifically refers to the rate at which two reactant molecules (A and B) collide in a given volume over a unit of time.

3. **Identifying the Role of ZAB**:
- In the context of the collision theory, `Z_(AB)` represents the collision frequency of reactants A and B. It quantifies how often the molecules collide with each other.

4. **Understanding Other Terms**:
- **Steric Factor (ρ)**: This is a factor that accounts for the geometry of the reacting molecules and is not represented by ZAB.
- **Rate Constant (k)**: This is a proportionality constant in the rate equation and is also not represented by ZAB.

5. **Conclusion**:
- Given the definitions and roles of the terms involved, we conclude that `Z_(AB)` specifically represents the collision frequency of reactants A and B.

### Final Answer:
`Z_(AB)` represents the collision frequency of reactants A and B in the collision theory of chemical reactions.

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