How do you relate reaction rate kinetics to chemical thermodynamics

[25 marks]

For the very large majority of chemical reactions, increasing the temperature increases the rate of the reaction. This is because nearly all chemical reactions have some activation barrier which must be surmounted before the reaction can proceed, and the added temperature helps to get over this barrier. There are however some processes which do not speed up with increased temperature, although there much fewer. The freezing of water is one obvious example.

Heating chemical substances can make the molecules separate and move around faster. This can increase the speed with which they mix with surrounding molecules from other chemical substances, thus speeding up a reaction. This is not always the case, some chemicals will only react when cold...

While it is true that hotter molecules move faster, it is not the improved mixing that makes reactions occur faster -- otherwise you could just stir more effectively and not have to heat! Heating gives the molecules more energy to surmount the activation energy barrier of the reaction. The more energy the reactants have, the more of them can surmount this barrier, which is required for the reaction to occur. The reason some reactions don't go faster when heated is because they do be activationless or the barrier may be so high that other methods are necessary to give the reactant sufficient energy to surmount the barrier.