Answer: 3. Molecules that are improperly oriented during collision will not react.
Step-by-step explanation:
According to the collision theory , the number of collisions that take place per unit volume of the reaction mixture is called collision frequency. The effective collisions are ones which result into the formation of products.
It depends on two factors:-
1. Energy factor: For collision to be effective, the colliding molecules must have energy more than a particular value called as threshold energy.
2. Orientation factor: Also the colliding molecules must have proper orientation at the time of collision to result into formation of products.
Thus not all collisions between reactant molecules lead to reaction because molecules that are improperly oriented during collision will not react.