What causes an increase in effective collisions without increasing average energy?

Catalysis

The correct answer is Option 3 : Catalysis

A catalyst increases the number of effective collisions by providing an alternative reaction pathway with lower activation energy. It does this without increasing the average kinetic energy of the reactant molecules.

• Option 1 : An increase in the reactant concentration → Increases collision frequency, but not specifically effective collisions through lowering activation energy.

• Option 2 : A decrease in pressure → Usually decreases collisions.

• Option 3 : Catalysis → Correct.

• Option 4 : An increase in temperature → Increases average kinetic energy of molecules.