Chapter 15 (Chemical Equilibrium) ! Rate of a chemical reaction: The amount of reactant that can be converted to product in a given period of time. ! A chemical reaction occurs through collisions between reactant molecules. o Rxn rate dependent upon number of sufficiently-high energy collisions that occur in a given time period. ! Ea = activation energy ! ∆E = Difference in stored chemical bond potential energy between reactants and productsFactors that affect reaction rate: 1) Concentration of reactants: a more concentrated reaction will be more likely to produce more reactant particle collisions (of sufficient energy to form activated complex) since there are MORE of them in a unit volume 2) Increasing temperature: 3) Addition of a catalyst: (Lowers activation energy of reaction)Chemical Equilibrium: (must rethink our concepts of reaction “directionality”) Dynamic Equilibrium: Rate of forward reaction is equal to the rate of reverse reaction. The Equilibrium Constant: Expresses a reaction’s equilibrium as a number • If a reaction’s Keq is very small, the equilibrium heavily favors reactants • If a reaction’s Keq is very large, the equilibrium heavily favors productsLeChatlier’s Principle: When a chemical system at equilibrium is subjected to change, the equilibrium shifts in a predictable way to compensate. • “Change” means alterations in temperature or reactant/product