Rate of Reaction

Understanding Rate of Reaction

  • The rate of reaction refers to the speed at which reactants are converted into products in a chemical reaction.
  • It can be expressed in terms of the change in concentration of a reactant or a product over time.
  • The faster the reactants are used up or the more rapidly products are formed, the higher the rate of reaction.

Factors Affecting Rate of Reaction


  • Increasing the temperature increases the rate of reaction.
  • This is because as temperature rises, particles move faster and collide more frequently and more energetically, resulting in more successful reactions.

Concentration and Pressure

  • Increasing the concentration of reactants in a solution or the pressure in a gas reaction also increases the rate of reaction.
  • Higher concentrations and pressures mean more particles in the same volume, leading to a higher chance of collisions and hence a faster reaction.

Surface Area

  • Increasing the surface area of solid reactants increases the rate of reaction.
  • Smaller particles or thinner pieces have a larger surface area exposed to other reactants, resulting in more frequent collisions and a quicker rate of reaction.


  • Catalysts are substances that increase the rate of reaction without being used up.
  • They provide an alternative reaction pathway with a lower activation energy, enabling more particles to react at a given temperature.

Measuring the Rate of Reaction

  • The rate of reaction can be measured by observing a change in quantity of a reactant or a product over time.
  • This could be tracking a change in mass, volume of gas produced, light transmission (for colour changes), or other observable factors.
  • To calculate the rate of reaction, you divide the quantity changed by the time taken.

Effect of Rate of Reaction on Industrial Processes

  • Understanding and manipulating rates of reaction is vital for economic and safety reasons in industrial processes.
  • Faster reactions can help achieve faster production rates, but they also consume reactants more rapidly and can be more hazardous due to the heat released.
  • Therefore, appropriate conditions and catalysts are often selected to optimise the speed, cost-effectiveness and safety of industrial chemical reactions.