EQUILIBRIUM

• chemical change involving interaction between

  substances of the electrons in their atomic, molecular or ionic structure.

  CHEMICAL REACTION
• 2 Types of Chemical Reaction:

  Reversible reaction

  Irreversible reaction
• Magnitude of change in the concentration of reactants or products per unit time

  REACTION RATE
• • rate or speed at which reactants are consumed or products are formed
  • also rate of chemical reaction or velocity of a chemical reaction
  • the amount of chemical change which takes place in a given interval of time usually expressed in unit of moles of substance used up or formed / liter of solution•unit time

  REACTION RATE
• Factors Which Influence the Speed of Reactions:

  1. nature of reacting substances
  2. concentration of reactants
  3. temperature
  4. presence of catalyst/s
  5. pressure
• • reaction that involves the formation of reactants from their original products
  • does not go to completion
  • A + B ⇌ C + D


  Reversible reaction
• Reversible reaction has 2 opposing reactions:

  • one proceeding to the products
  • the other, the products recombining to produce the initial reactants
• • the products are not capable of forming the

  reactants

  • goes to completion
  • A + B → C + D


  Irreversible reaction
• Evidences of Irreversible reaction

  1. when a gas is formed / formation of bubbles
  2. when water droplets are formed
  3. when an insoluble precipitate is formed
• The more reactive the reactants , the faster

  is the reaction rate

  Nature of reacting substances
• What do Active metals do?

  They displace hydrogen vigorously and rapidly from acids, while less active metals act slowly
• It combines very slowly with other elements

  Nitrogen is inert
• Combine with most of the other elements readily

  Halogens
• Increases in the concentration of reactants,

  increases the rate of formation of products

  Concentration of reactants
• Increase in temperature will speed up an endothermic reaction and slows down an exothermic reaction


  Temperature
• Types of catalyst/s

  1. positive catalyst
  2. negative catalyst
• Increase the rate of a reaction

  Positive catalyst
• Reduces the rate of reaction

  Negative catalyst
• Affects only gaseous systems

  Pressure
• • state at which two opposing reactions proceed at the same rate
  • only reversible reactions attain chemical equilibrium
  • a state of reversible reaction where the rates of forward and backward reactions are equal at chemical equilibrium: rate of forward reaction = rate of backward reaction
  • Rf = Rb
  • A + B ⇌ C + D


  CHEMICAL EQUILIBRIUM
• Concepts of Equilibrium

  • Law of Mass Action ( Guldberg and Waage)
  • Law of Chemical Equilibrium
  • LE CHATELIER’S PRINCIPLE
• • states that the rate of a chemical reaction is directly proportional to the molar concentration of the reactants each raised to a number equivalent to the corresponding coefficient in the balanced chemical equation


  Law of Mass Action
• • states that for a reversible chemical reaction, at a fixed temperature and in a state of equilibrium, the product of the formula
  • weight concentrations of substances formed in the reaction divided by the product of the formula – weight concentrations of the reactants, each raised to the power indicated by the number of molecules or ions in the balanced equation is equal to a CONSTANT.


  Law of Chemical Equilibrium
• • states that when a stress is applied to a system in equilibrium whereby the equilibrium is altered, the equilibrium will shift in such a manner as to relieve or neutralize the effect of the added stress.


  LE CHATELIER’S PRINCIPLE
• Change in temp (inc) supply of heat to the system

  Stress
• Le Chatelier's Principle


  "Restoring Balance"
• Tree types of Stresses:

  • Concentration changes
  • Temperature changes
  • Pressure changes
• FACTORS AFFECTING A SYSTEM AT CHEMICAL EQUILIBRIUM

  • Concentration
  • Temperature
  • Pressure
• An increase in concentration of the reactants will cause the equilibrium to shift to the right; it is to the left when the concentration of the reactants are decreased

  Concentration
• For endothermic reactions, an increase in temperature will cause the equilibrium to shift to the right, a decrease in temperature will produce a shift to the left. The opposite is expected for exothermic reactions


  Temperature
• Applicable only to gaseous systems ( mole = volume)

  Pressure
• A substance that influences the speed of a chemical

  Catalyst
• Cannot change the numerical value of the equilibrium constant and hence the relative amounts of reactants and products present at equilibrium. However, it may greatly reduce the time necessary for the establishment of equilibrium

  Catalyst
• Positive catalyst


  True catalyst
• Negative catalyst


  Inhibitor
• It is the product of the molar concentrations of the product for a chemical reaction, each raised to the power of the respective coefficient in the equation, divided by the product of the molar concentration of the reactants each raised to the power of the respective coefficient in the equation.

  EQUILIBRIUM CONSTANTS