Factors Affecting Rate and Measuring Rate Experimentally

Building on collision theory, we can predict and explain how several controllable variables change the rate of a reaction. Each factor works by altering the frequency of collisions, the fraction that are successful, or both.

Concentration. Increasing the concentration of a dissolved reactant places more particles in each cubic decimeter of solution. Particles are then closer together on average, so collisions occur more frequently and the rate rises. For most reactions, doubling a reactant concentration increases the rate, though the exact proportionality depends on the reaction's order, which we treat later.

Pressure (for gases). Increasing the pressure of a gaseous system by compressing it into a smaller volume is essentially the gas-phase equivalent of raising concentration. The same nu