Introduction to Rate Law

The Rate Law is an expression which shows the relationship between the rate of a chemical reaction and the concentrations of the reactants. It is usually written in the form R=k[A]^m[B]^n.
Here, R, is the rate of reaction, k is the rate constant, and [A] and [B] are the molar concentrations of the reactants.
The exponents m and n represent the order of reaction with respect to each reactant and describe how the rate changes with a change in their concentrations.

Understanding the Order of Reaction

The order of reaction with respect to a particular reactant shows how the rate of reaction changes if the concentration of that reactant is changed.
Zero Order: If the reaction is zero order with respect to a reactant, the rate of reaction does not change if the concentration of that reactant is changed.
First Order: If the reaction is first order with respect to a reactant, the rate of reaction changes proportionally with the concentration of that reactant.
Second Order: If the reaction is second order with respect to a reactant, the rate of reaction changes with the square of the concentration of that reactant.
The rule of multiplying concentrations can deduce the overall order of a reaction.

The Rate Law and reaction order cannot be determined from the stoichiometric equation of a reaction, they need to be determined experimentally.
Techniques such as method of initial rates or rate measurements at different concentrations are used to determine the rate law.
The Rate Constant (k) is specific to a given reaction at a given temperature and can also be determined experimentally.

Understanding the Rate Law allows us to predict how the rate of a reaction will change under different conditions.
It is useful in industrial production processes to optimise conditions for maximum reaction rate and streetwise yield.
Understanding rate law can also aid in the discovery and development of new chemical reactions and catalysts.