Rate of Reaction

Understanding Rate of Reaction

  • Rate of Reaction denotes the speed at which reactants transform into products in a chemical reaction.
  • It is usually measured by the change in concentration of the reactant or product over time, given as mol/dm³/s.
  • A high rate of reaction indicates that the reaction completes quickly.
  • Conversely, a low rate of reaction suggests the reaction takes a longer time to finish.

Factors Influencing Rate of Reaction

  • Temperature: Increasing the temperature increases the speed of the particles, leading to more collisions and hence a faster rate of reaction.
  • Concentration or Pressure: A higher concentration of reactants or higher pressure (for gases) means more particles in a specific volume, leading to increased frequency of collisions.
  • Surface Area: Increasing the surface area of a solid reactant results in a higher rate of reaction as more particles are exposed for collisions.
  • Catalysts: Catalysts speed up reactions by providing an alternative reaction pathway with a lower activation energy.

Collision Theory

  • Collision theory explains how various factors influence the rate of reaction.
  • For a reaction to occur, particles must collide with sufficient energy (activation energy) and the correct orientation.
  • A successful collision that leads to a reaction is known as an effective collision.

Rate Equations and Orders of Reaction

  • The rate equation expresses the rate of a reaction in terms of the concentrations of the reactants.
  • It often has the form: rate = k[A]¹[B]² where A and B are reactants, k is the rate constant, and the exponents 1 and 2 represent the order of reaction with respect to A and B.
  • A reaction’s order with respect to a reactant regulates how the rate is affected by the concentration of that reactant.
  • The overall order of a reaction is found by adding the orders for each reactant as specified in the rate equation.

Rate of Reaction in Industry

  • Understanding the rate of reaction is essential in optimising industrial processes for efficiency and safety.
  • Industrial processes require controlling the rate of reaction to meet production demands and to prevent accidents caused by excessively fast reactions.
  • Processes can be designed to maximise yield, minimise the formation of unwanted by-products, and ensure the process is completed within an acceptable time frame.
  • The choice and utilisation of suitable catalysts, suitable temperatures, and pressures are all important in controlling the rates of industrial reactions.