Kinetics and Equilibrium

Kinetics The study of the mechanisms of a reaction and the rates of reaction. ****** A reaction is at Equilibrium when: The rate of the forward reaction is EQUAL to the rate of the reverse reaction

Kinetics The study of the mechanisms of a reaction and the rates of reaction. ****** A reaction is at Equilibrium when: Concentration of Reactants and Products are CONSTANT NOT EQUAL!!!!!!!!!!!!!!!!!!!!!!

Factors that effect Rate of Reaction (R of R) Collision Theory Anything that will increase the number of and frequency of the collisions More effective collisions

Factors that Effect Rates of Reactions (T,A,P,S,C,N) Temperature -(Average Kinetic Energy=motion) Inc. Temperature = Increase R of R Amount Increase Amount (concentration) = Increase R of R Pressure (g only) - Inc Pressure = increase R of R Surface Area – Inc. S.A. = Inc. R of R Nature of Reactants (Ionics > Covalents) Due to their reactivity and the number of bonds needed to break

Catalyst – anything that is added that will increase the R of R If present will increase the R of R How? By providing an alternative pathway for the Reaction by effecting (Lowering) 3 things Ea of the Forward Catalyzed Reaction Ea of the Reverse Catalyzed Reaction PE of the Activated complex

Two Kinds of Reactions Endothermic Absorb Energy Heat + AB  A +B Heat is a reactant Break Bonds + H Exothermic Release Energy A + B  AB + Heat Heat is a product = Stability Bond formation - H

(Most Effective Collisions)

PE of the Activated Complex (Most Effective Collisions) PE of the Reactants PE of the Products PE of the Activated Complex (Most Effective Collisions) Ea =Activation Energy of forward Rxn (The minimum amount of energy needed to start a reaction to completion) Ea of the Reverse Rxn NOTE: Endo > Exo therefore Exo is more spontaneous H (Heat of Reaction- Enthalpy) H = Hproducts – Hreactants + H = Endothermic - H = Exothermic

Entropy S Entropy is defined as the degree of randomness, disorder, chaos (s) – (l) – (aq) – (g)

Gibbs Free energy G A reaction will always proceed spontaneously if the sign for Gibbs free energy is (-) - G The two conditions that favor a - G are : low energy - H Exothermic high entropy + S

LeChatelier’s principle States that when a system that is at equilibrium is placed under a stress, the systems equilibrium will shift in order to relieve the stress Inc. (T) : will always favor endothermic reactions Inc (P) : will always favor the side of less mole formation

A + B C + D Equilibrium

N2 3H2 NH3 HEAT

CH4 3H2 CO2 H2O HEAT