Defining the Rate Law
A rate law is a mathematical expression that describes the relationship between the rate of a chemical reaction and the concentration of its reactants. It shows how changes in the amount of reactants will affect the speed at which the reaction proceeds.
Section 2: The Rate Law Equation
The general form of a rate law is: Rate = k[A]^m[B]^n. In this equation, 'k' is the rate constant, which is specific to the reaction and temperature. '[A]' and '[B]' represent the molar concentrations of the reactants. The exponents 'm' and 'n' are the reaction orders, which indicate how sensitively the rate depends on the concentration of each reactant.
Section 3: A Practical Example
Consider the reaction 2NO(g) + O₂(g) → 2NO₂(g). Through experiments, the rate law is found to be Rate = k[NO]²[O₂]. This tells us that if we double the concentration of NO, the reaction rate will increase by a factor of four (2²), and if we double the concentration of O₂, the rate will double.
Section 4: Why Rate Laws Are Important
Rate laws are crucial in chemistry for predicting how quickly a reaction will occur under different conditions. They provide valuable insights into the reaction mechanism, which is the step-by-step sequence of elementary reactions by which overall chemical change occurs. This understanding is essential for optimizing industrial chemical processes and studying biological pathways.