Progress of Chemical Reactions - PowerPoint PPT Presentation

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Progress of Chemical Reactions

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Progress of Chemical Reactions Rate Laws An expression for the rate of a reaction in terms of the concentrations of the reactants Equation: A B rate = k[A] k is a ... – PowerPoint PPT presentation

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Title: Progress of Chemical Reactions


1
Progress of Chemical Reactions
2
Rate Laws
  • An expression for the rate of a reaction in terms
    of the concentrations of the reactants
  • Equation A ? B rate kA
  • k is a constant

3
Rate Constant
  • Specific rate constant (k) a proportionality
    constant relating the concentration of the
    reactants to the reaction rate
  • k is large is the products form quickly
  • k is small is the products form slowly

4
Order of Reaction
  • First order reactions the reaction rate is
    directly proportional to the concentration of one
    reactant
  • The exponent for that reactant is 1
  • Half the concentration, half the rate
  • Rate kAB
  • Reaction is first order in A and B

5
First Order Reaction
6
Order of Reactions
  • Reactions can be second or third order, with the
    reactants raised to the power of 2 3
    respectively.
  • Order of reaction is determined experimentally.
  • 9 out of 10 coefficient will be the exponent
  • aA bB ? cC rate AaBb
  • Overall order of the reaction is the sum of the
    exponents for the individual reactants
  • 2N2O ? 2N2 O2 rate N2O2
  • Overall order 2
  • 2N2 O2 ? 2N2O rate N22O2
  • Overall order 3

7
Second Order Reactions
8
Reaction Mechanisms
  • Elementary Rxn
  • Reactants? Products in 1 step
  • 1 activation energy peak
  • Reaction Mechanism series of elementary
    reactions
  • Reaction progress is a series of peaks and valley
  • Peaks activation energy
  • Valley energy of intermediates
  • Intermediate product of the steps in the
    reaction mechanism
  • N2O ? N2 O
  • N2O O ? N2 O2
  • 2N2O ? 2N2 O2

9
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10
Reaction Mechanisms
11
Reaction Mechanism
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