che 102 (unit 3)

what conditions must be met for a chem rxn to occur (collision theory)

molecules must collide with sufficient energy in correct orientation

1. molecular collisions

2. activation energy →avg activation energy = minimum energy for key bonds to break

3. collision orientation

what is activation energy?

energy level that reactant molecules must achieve for a rxn to take place (i.e. for key bonds to break)

what is an activated complex?

hypothetical transitory species → can return back to og reactants or form products

formed when sufficiently energetic reactants collide

catalysts (what it does, how, why, types)

what/how: increases rate of rxn by providing a different rxn path with lower Ea (and diff activated complex)

• participates in rxn but NOT altered (does not appear in overall chem rxn)

why: alternative for high temps that would be necessary for rxn with high Ea

types: homogeneous (same phase as reactants) or heterogeneous (diff phase)

favorable and unfavorable collision orientation

what can affect reaction rate and why

concentration of reactants →inc reactant molecules in same volume=inc collision probability

rxn temp → inc temp=inc avg kinetic energy of reactants (inc speed)=inc collision frequency

presence of catalysts → provides diff rxn pathway with lower Ea

physical nature of reactants → gas>liquid>solid, higher surface area

rate of reaction equation

change in concentration over change in time

volumetric rate of reaction equation

divide rate of rxn equation by system volume to get rate of rxn per unit volume

rate of reaction for generic equation aA+bB → cC + dD

how must a rxn rate be determined

experimentally (empirically)

what is a differential rate law and when is it used

what is an integrated rate law and when is it used?

zero order rxn, rxn rate eqns

first order rxn, rxn rate eqns

second order rxn, rxn rate eqns

what is the arrhenius eqn and when is it used?