Question

Can someone in a simple manner explain in terms of collision theory, how increasing temperature affects the rate of a reaction?

Answer 1

molecule moving faster !

Answer 2

Temperature \(\propto\) velocity

Answer 3

A higher temperature means molecules are moving faster. This affects reaction rate two ways: first, it means molecules collide more often, which means reactive collisions (collisions during which a chemical reaction occurs) are more frequent. Secondly, and much more importantly, it means that a larger fraction of the collisions are hard enough that the activation energy to get the reaction going can be supplied.

What you should keep in mind is that molecules moving at the average speed at roughly room temperature, or even a hundred or so degrees above room temperature, don't have nearly enough energy to react. The average kinetic energy of molecules at an absolute temperature T goes like RT, where R = the gas constant. At room temperature that's about 2.5 kJ/mol. To get a chemical reaction going, you must usually supply at least as much energy as is needed to break a chemical bond, which is of order 100-500 kJ/mol, 50-100 times greater. That means only the molecules moving of order ten times faster than the average have enough energy to react. The most important effect of raising the temperature is to cause the fraction of molecule that are moving at very high speeds to increase.