Effective collision s are those in w hich molecules must:

Options

A. Have energy equal to or greater th an the threshold energy
B. Have proper orientation
C. Acquire the energy o f activation
D. All of these

Explanation

To determine the criteria for effective collisions in chemical reactions, we can break down the requirements into clear steps:

### Step-by-Step Solution:

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

2. **Sufficient Energy**:
- For a collision to be effective, the colliding molecules must possess sufficient energy. This energy must be equal to or greater than the activation energy (the minimum energy required for a reaction to occur).

3. **Proper Orientation**:
- In addition to having sufficient energy, the molecules must collide in a specific orientation. The correct orientation allows the necessary bonds to break and form during the collision, leading to product formation.

4. **Threshold Energy**:
- The energy of the colliding molecules must meet or exceed the threshold energy required for the reaction. This is closely related to the concept of activation energy.

5. **Conclusion**:
- Therefore, effective collisions require:
- Sufficient energy (activation energy).
- Proper orientation of the colliding molecules.
- Energy equal to or greater than the threshold energy.

6. **Final Answer**:
- The answer to the question is that effective collisions are those in which molecules must have sufficient energy, proper orientation, and meet the threshold energy requirement. Thus, the correct choice is **all of these**.