Chemical kinetics is the study of the rates of chemical reactions. The collision theory describes how chemical reactions occur in terms of potential energy. For a chemical reaction to occur, molecules or atoms must collide at correct orientation and at sufficient energy. Any factor that increases the number of collisions or energy of collisions will increase the reaction rate. The rates for chemical reactions are often proportional to the initial concentrations of the reactants raised to a power. The proportionality constant is the rate constant. The rate constant varies with temperature. The Arrhenius equation relates the rate constant with temperature. A chemical reaction can occur in a single step or in multiple steps. For reactions with multiple steps, the rate of the slowest step determines the rate of the overall reaction.
At A Glance
- Chemical kinetics is the field that studies the rates of chemical reactions. The speed at which a reaction occurs is its reaction rate.
Collision theory explains how chemical reactions occur. The molecules or atoms colliding must have a minimum amount of energy and a specific orientation for a chemical reaction to take place.
- The rate law relates the rate of a reaction with the concentrations of reactants.
Reaction order is the sum of the powers that the concentrations of the reactants are raised to.
- Colliding molecules or atoms must have a minimum amount of energy for a chemical reaction to occur. Temperature is a measure of the energy of reactants. The Arrhenius equation provides a relationship between rate constant and temperature.
- A reaction mechanism may involve a single step or multiple steps. A reaction that occurs in a single step is an elementary reaction.
Some chemical reactions occur in more than one step. The slowest step, known as the rate-determining step, determines the rate of the reaction.
- The rate of a chemical reaction increases by using a catalyst to lower the activation energy.
Integrated rate laws allow reaction rate to be defined as a function of time instead of initial concentrations.