Two reactions those are very slow and two reactions those are very fast have to be identified.
Rate of a reaction: It represents the speed at which a chemical reaction runs. How much concentration of substrates (reactants) consumed and how much concentration of targets (products) formed in a unit of time is said to be rate of reaction. By using rate of reaction we can classify the two types of reactions, those are as follows.
Slow reaction: In slow reactions the rate of reaction is very slow. It means the conversion of substrates (reactants) to targets (products) takes long time over days, even years also.
Fast reaction: In fast reactions the rate of reaction is very high. It means the conversion of substrates (reactants) to targets (products) takes very less time over in seconds, minutes or hours.