Rate Law

The rate law links how fast a reaction proceeds to the current concentrations of reactants through a constant of proportionality, k, and concentration exponents m and n. Those exponents are the reaction orders and usually reflect the reaction mechanism or are determined experimentally, because the overall balanced equation alone does not generally reveal them. As concentrations change, the frequency of effective reactant encounters changes, so the rate changes in a predictable power-law way for many elementary and empirically fitted reactions.

Use this when you need to model or analyze how a reaction rate depends on measured reactant concentrations, especially in kinetics experiments. It is also used to determine reaction orders, predict rate changes after a concentration shift, and compare kinetic data for proposed mechanisms.

• Assuming m and n come from the balanced equation instead of experimental kinetic data
• Confusing the rate constant k with the reaction rate, which changes as concentrations change
• Forgetting to raise each concentration to its correct order, especially when an order is zero, fractional, or negative