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6.5 Rate Law

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.

AV

6.5 Rate Law

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.

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