1) Calculating rates of reactions

• Rate of reaction = Amount of reactant or product formed / time
• One way rate of reaction can be found Measuring the amount of reactants used:

  • If one of the products is a gas, measure the mass in grams (g) of the reaction mixture before and after the reaction takes place and the time it takes for the reaction to happen.
  • The mass of the mixture will decrease.
  • The units for the rate of reaction may then be given as g/s.
• The amount of a reactant can also be measured in moles (mol).
• As the reaction takes place the reactant is used up, so the amount of reactant remaining decreases.
•  The concentration of the reactant is calculated as the amount (mol) divided by the volume of the reaction mixture (dm3). It is measured in units of mol/dm3.
•  Measuring the amount of products formed:

  • If one of the products is a gas, measure the total volume of gas produced in cubic centimetres (cm3) with a gas syringe and the time it takes for the reaction to happen.
  • The units for the rate of reaction may then be given as cm3/s.
• Measuring the time it takes for a reaction mixture to become opaque or change colour:

  • Time how long it takes for the mixture to change colour.
• Rate of reaction=

  1 / time taken for solution to change colour