Lecture 9 (1/28/13)
• PseudoFirst Order Reactions:
o All reactants but one are present at such high concentrations that they do
not change significantly during the course of reaction
o Reaction rate is determined by the concentration of the limiting reactant.
• Factors Affecting Reaction Rate:
o Concentration of reactants:
Increased frequency of collisions.
Defined by rate law.
o Energy of collisions:
Energy needed to break bonds in reactants, allowing new bonds to
o Orientation of colliding molecules
Increased temperature increases kinetic energy of molecules,
o Activation Energy (a ):
Minimum energy of molecular collisions required to break bonds
in reactants, leading to formation of products.
o These factors incorporated into rate constant k by Arrhenius
• Arrhenius Equation:
o R = universal gas constant (in J/mol∙K).
o T = temperature (in