CO5

• Chemical Equilibrium

  All chemical reactions are reversible

  Many reactions lead to incomplete conversion of reactants to products

  State reached by a reaction mixture when the rates of forward = reverse reactions
• Dynamic Equilibrium

  Systems in which the forward and reverse processes are still occurring

  represented by writing a double arrow symbol (⇄)
• Chemical reactions always proceeds spontaneously toward equilibrium
• Products > Reactants

  product favored

  ->
• Products < Reactant

  reactant favored

  <-
• Equilibrium Constant

  values of K are dimensionless
• Reactions Involving Solids

  concentrations of any solid reactants and products are not included in the equilibrium constant expression
• Reactions in Solution

  concentration of water is not included in the equilibrium constant expression

  liquid state
• K > 1

  product-favored or forward-favored

  concentrations of products > concentrations of the reactants at equilibrium
• K < 1

  reactant-favored or backward-favored

  concentrations of reactants > concentrations of the product at equilibrium
• Reaction Quotient

  will tell you whether a system is at equilibrium (Q = K) or is not at equilibrium (Q ≠ K)

  predict what changes will occur in reactant and product concentrations as the reaction proceeds to equilibrium
• Q < K

  some reactants must be converted to products for the reaction to reach equilibrium

  product reaction or forward reaction is favored
• Q > K

  some products must be converted to reactants for the reaction reach equilibrium

  reactant reaction or backward reaction is favored
• Q = K

  the reaction mixture is in equilibrium
• Le Chatelier’s Principle

  a change in any of the factors that determine the equilibrium conditions of a system will cause the system to change to reduce or counteract the effect of the change
• Chemical Equilibrium

  can be disturbed or changes of conditions (stresses) that may affect the point of equilibrium and cause the system to compensate
• Three ways on how you can disturb a chemical equilibrium

  Change in concentration of a reactant or product

  Change in the partial pressure of gaseous reactants and products by changing the volume

  Change in temperature
• Addition of reactant

  Product concentration increases (shift forward)
• Addition of product

  Reactant concentration increases (shift backward)
• Removal of reactant

  Product concentration decreases (shift backward)
• Removal of product

  Reactant concentration decreases (shift forward)
• Decrease in volume, increase in pressure

  Smaller number of molecules will be favored
• Increase in volume, decrease in pressure

  Larger number of molecules will be favored
• Endothermic - If temperature increases

  Forward reaction will be favored
• Endothermic - If temperature decreases

  Backward reaction will be favored
• Exothermic - If temperature increases

  Backward reaction will be favored
• Exothermic - If temperature decreases

  Forward reaction will be favored
• Arrhenius

  any substance which ionizes in water to produce:

  Protons is an Acid

  Hydroxide ions is a Base
• Acid

  Hydronium ions (H3O+ ) in water are acidic
• Base

  Hydroxide ions (OH- ) in water are basic
• Brønsted-Lowry Base

  Proton acceptor
• Brønsted-Lowry Acid

  Proton donor
• Strong acids and bases almost completely ionize
• Weak acids and bases do not fully ionize
• Water is amphiprotic

  it can donate or accept a proton (act as acid or base)
• Acidic Solution

  pH < 7.00

  lower pH = more acidic
• Basic Solution

  pH > 7.00

  higher pH = more basic
• Buffer

  chemical system that resists changes in pH
• Buffer must contain

  A weak acid to react with any added base

  A weak base to react with any added acid

  These components must not react with each other