Which statement regarding chemical reactions is true according to collision theory?

• A. All molecular collisions result in chemical equations.
• B. Increasing the temperature of a reaction decreases the kinetic energy of molecules, making collisions more effective.
• C. Catalysts make individual collisions more effective, increasing reaction rates.
• D. Proper orientation of molecules is required for collision to result in chemical reactions.

Answer: (D)

In collision theory, a reaction occurs only when reacting molecules collide with enough energy to overcome the activation barrier and with the proper orientation of their reactive parts. Even when energy is sufficient, if the molecules strike each other in the wrong geometry, bonds won’t break and new bonds won’t form, so no reaction happens. This is why orientation matters: it determines whether the electrons and orbitals involved can rearrange to form products.

The statement about proper orientation being required is the best reflection of this idea. It captures the fact that not all collisions lead to products, and orientation is a key gatekeeper for whether a collision can be successful.

Misleading choices either flip energy behavior (temperature increases kinetic energy, not decreases) or generalize catalysts too much. Catalysts don’t make each collision more effective in isolation; they provide an alternative, lower-energy pathway that increases the fraction of collisions that lead to products, effectively speeding up the reaction without changing the fundamental orientation requirement for every collision.