Rate Law Equation

• Reactant concentrations determine how quickly a reaction proceeds (reaction rate)

• Reaction rate can be expressed mathematically in a rate law equation:

• Where:

  • k = rate constant (unique for every reaction, must be determined experimentally)

  • m and n (maybe p) = order of reaction (describes relationship between rate and concentration of reactant)

Order of Reaction

• 1st order (1)

  • Rate is directly proportional

• 2nd order (2)

  • Rate is exponentially proportional

• 0 order (0)

  • Rate is NOT related (changing concentration does NOT affect rate)

Determining order of reaction

• Using experimental data for instantaneous reaction rate just after t=0 (when products are insignificant), compare rates where ONE reactant is changed and others are kept constant

  • IF rate does NOT change when reactant is doubled, order is 0

    • Rate = [A]0

  • IF rate doubles when reactant is doubled, order is 1

    • Rate = [A]1

  • IF rate quadruples when reactant is doubled, order is 2

    • Rate = [A]2

• TOTAL ORDER OF REACTION IS EQUAL TO THE SUM OF ALL EXPONENTS IN RATE LAW EQUATION.