Question

The central idea of the collision model is that molecules must collide in order to react. Give two reasons why not all collisions of reactant molecules result in product formation.

Short answer

One reason why not all collisions between reactant molecules result in product formation is insufficient energy. The colliding molecules may not have enough energy to overcome the activation energy barrier, which is the minimum energy required for a reaction to occur. Another reason is the incorrect orientation of the colliding molecules. A productive collision requires the reactant molecules to collide in a specific orientation that allows their atoms to rearrange and form new bonds, leading to the formation of products. If the orientation is not appropriate, the reaction will not proceed.

Step-by-step solution

Reason 1: Insufficient energy

One reason why not all collisions between reactant molecules result in the formation of products is that the colliding molecules may not have enough energy to overcome the activation energy barrier. Activation energy is the minimum energy required for a reaction to occur; if the colliding molecules' combined kinetic energy is less than the activation energy, the reaction will not proceed and the molecules will simply bounce off each other.

Reason 2: Incorrect orientation

Another reason why not all collisions between reactant molecules result in the formation of products is that the molecules may not collide in the proper orientation. A productive collision requires the reactant molecules to collide in such a way that their atoms can rearrange and form new bonds (leading to the formation of products). If the orientation of the colliding molecules is not appropriate for this rearrangement to occur, the reaction will not proceed and the molecules will separate without reacting.