Chemical Kinetics – Notes
Rate of a Chemical Reaction
Chemical kinetics is the part of physical chemistry that studies reaction rates and explains why certain reactions are instantaneous and others are not. It also describes the conditions in which reaction rates can be altered.
In chemical kinetics, the rate of chemical reaction is defined as the rate of decrease in the concentration of one of the reactants, or the rate of increase in the concentration of one of the products.
The rate of reaction is always taken as the change in the concentration of reactants or products in a definite interval of time. This is called the average rate of a chemical reaction.
The rate of a reaction determined a particular instant of time is called the instantaneous reaction rate.
If the concentration is in mol L-1, then the unit for rate of reaction is mol L-1 S-1.
Effect of Concentration on Rate, Order of a Reaction
Rate law is the expression in which the rate of reaction is given in terms of the molar concentrations of the reactants, with each concentration being raised to some power, which may or may not be the same as the stoichiometric coefficients of the reacting species in a balanced chemical equation.
The order of a reaction is defined as the sum of the powers of the concentration terms in the rate law.