The rate of a chemical reaction is defined as the change in concentration of reactants or products over time. The law of mass action states that the rate of a chemical reaction is proportional to the product of the concentrations of the reactants, each raised to the power of its stoichiometric coefficient.
For a general chemical reaction,
aA + bB → cC + dD
The rate of this reaction can be expressed using the law of mass action as:
Rate = k[A]^a[B]^b
Where:
- Rate is the rate of the reaction in M/s.
- k is the rate constant of the reaction in M^-a-b*s^-1.
- [A] and [B] are the concentrations of the reactants A and B in M.
- a and b are the stoichiometric coefficients of the reactants A and B.
This equation shows that the rate of the reaction is directly proportional to the concentrations of the reactants, with the proportionality factor being the rate constant. The rate constant is a constant for a given reaction at a given temperature and pressure.
The law of mass action can also be used to derive rate expressions for more complex reactions, such as those involving multiple reactants or products, and those that occur in multiple steps.
