The branch of chemistry , which deals with the rate of chemical reactions . the factors affecting the rate of reactions and the mechanism of the reaction . is called chemical kinetics .
Chemical Reactions on the Basis of Rate of Reaction
1 . Fast / instantaneous reactions Chemical reaction which completes in less than Ips ( 10 -12 s ) time , IS known as fast reaction . It IS practically impossible to measure the speed of such reactions , e . g ., ionic reactions . organic substitution reactions .
2 . Slow reactions Chemical re actions which completes in a long time from some minutes to some years are called slow reactions . e . g ., rusting of iron . transformation of diamond etc .
3 . Moderately slow reactions Chemical reactions which are intermediate between slow and fast reactions are called moderately slow reactions .
Rate of Reaction
Rate of a chemical reaction IS the change in the concentration of any one of the reactants or products per unit time . It is expressed in mol L -1 s -1 or Ms -1 or atm time -1 units .
Rate of reaction = ( decrease / increase in the concentration of reactant / product / time taken )
This rate of reaction is known as average rate of reaction ( rav ).( rav can be calculated by dividing the concentration difference by the time interval ).
For a chemical reaction ,