Which statement correctly expresses collision theory?

• A. Chemical reactions occur when reactant particles are present in equal concentrations.
• B. Chemical reactions occur only when reactant particles collide with any energy.
• C. Chemical reactions occur spontaneously without the need for particle collisions.
• D. Chemical reactions occur when reactant particles collide with sufficient energy and proper orientation.

Answer: (D)

Verified step by step guidance

1. Understand that collision theory explains how chemical reactions occur at the molecular level by focusing on particle collisions.
2. Recognize that for a reaction to happen, reactant particles must collide; however, not all collisions lead to a reaction.
3. Identify two key conditions for effective collisions: the particles must collide with sufficient energy (called activation energy) and with the correct orientation to break and form bonds.
4. Note that simply having reactants in equal concentrations or any collision energy is not enough to guarantee a reaction.
5. Conclude that the correct expression of collision theory is that chemical reactions occur when reactant particles collide with sufficient energy and proper orientation.