Speed of Reaction

The speed of reaction (rate of reaction) is important in the chemical industry and everyday life as it measures how fast the reaction takes place.

Different reactions occur at different speeds.

  • The higher the speed of reaction, the faster the rate of manufacturing large amounts of required products.
  • Example of a reaction with a slow speed of reaction: Rusting of iron
  • Example of a reaction with a fast speed of reaction: Burning of paper

The substances that are used in a chemical reaction are called the reactants and the substances produced in the reaction are called the products.

During a chemical reaction, the following things will happen:

  • the quantity of reactants will decrease with time
  • the quantity of products will increase with time

Hence, we can determine the speed of the reaction by measuring:

  • the rate at which the reactants are being used up; or
  • the rate at which the products are being produced.

This leads us to the important definition for speed of reaction:

The speed of reaction is defined as the amount of reactants converted to products formed per unit time.

Some of the suitable observable changes that allows us to measure the rate at which the reactants are being used up or the rate at which the products are being produced are:

  • A change in mass during the reaction (E.g. Due to a change in state from liquid to gaseous)
  • A change in the volume of air in the reaction chamber
  • Formation of a precipitate
  • pH value of an aqueous solution
  • Temperature changes
  • Colour changes

Some common factors that affect the speed of reaction are:

  • Pressure
  • Temperature
  • Presence of a catalyst
  • Concentration of reactants used
  • Surface area of reactants used

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