Question

For a certain reaction large fraction of molecules has energy more than the threshold energy, yet the rate of reaction is very slow. Why?

Answer 1

According to collision theory apart from the energy considerations, the colliding molecules should also have proper orientation for effective collision. This condition might not be getting fulfilled in the reaction as it shows the number of reactants taking part in a reaction, which can never be zero.

Though the reacting molecules may be having energy more than threshold energy, yet they may not be effective due to lack of proper orientation.