Chemistry

• Dynamic equilibrium


  Equilibrium in terms of concentrations and rate
• Equilibrium Constant


  1. Write

  2. Calculate

  3. Manipulate
• Le Chatelier's Principle


  • Changes in concentration, pressure, or temperature can disturb the equilibrium and lead to a shift in the equilibrium position
• Position of equilibrium


  The relative amounts of reactants and products present at equilibrium
• Equilibrium doesn't mean that there are 50% reactants and 50% products
• Equilibrium shift to the right

  Favors the forward reaction, more products are made
• Equilibrium shift to the left

  Favors the backward reaction, more reactants are made
• Changes made to a reaction at equilibrium

  1. Changes to the concentrations of reactants and products

  2. Changes to the pressure of a system involving gaseous reactants and products

  3. Changes to the temperature
• Videos


  • https://youtu.be/7zuUV455zFs
  • https://youtu.be/XhQ02egUs5Y
• If hydrogen is added

  The equilibrium will shift to the right, causing the concentrations of hydrogen and nitrogen to decrease and the concentration of ammonia to increase
• If ammonia is removed

  More nitrogen and hydrogen will react to replace the ammonia that has been removed, the equilibrium position will shift to the right (the products side)
• Increasing concentration


  Sends the equilibrium towards the opposite side
• Decreasing concentration


  Sends the equilibrium towards the same side
• If pressure is increased

  The equilibrium position will shift to the side with the lowest number of gaseous molecules
• If pressure is decreased


  The equilibrium position will shift to the side with the greatest number of gaseous molecules
• If temperature is increased

  The equilibrium position will shift in the endothermic direction
• If temperature is decreased


  The equilibrium position will shift in the exothermic direction
• A catalyst increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy
• The presence of a catalyst has no effect on the equilibrium position because a catalyst increases the rate of both the forward and reverse reactions by the same amount
• Changes and their effect on equilibrium

  • Concentration of SO2 increased
  • Concentration of O2 decreased
  • Concentration of SO3 decreased
  • Pressure increased
  • Temperature increased
• Reversible Reactions


  Reactions where the reactants react to form products, which can then revert back into the original reactants
• Reversible Reactions


  1. Forward reaction: Reactants react to form products

  2. Backward reaction: Products react to form back the reactants
• Examples of Reversible Reactions


  • Heating blue hydrated copper sulphate to produce white anhydrous copper sulfate and water, then adding water to the white copper sulfate to form back the blue hydrated copper sulfate
  • Ammonium chloride decomposing upon heating to make ammonia and hydrogen chloride, which then react at the cold mouth of the tube to make back ammonium chloride
• Irreversible Reactions


  Reactions where the reactants react to form products, which cannot revert back into the original reactants
• Combustion of fuel, cooking and countless of irreversible chemical reactions are happening right now in your body
• Dynamic Equilibrium


  • Forward and reverse reactions take place continuously (the reaction doesn't stop)
  • It must be in a closed system
  • Temperature must be kept constant through equilibrium
  • Rate of the forward reaction is equal to the rate of the backward reaction
  • Concentrations of reactant and products are kept constant
• Open System


  A system that exchanges both energy and matter with its surroundings
• Closed System


  A system that exchanges only energy with its surroundings, not matter
• Equilibrium Conditions


  1. Rate of forward reaction decreases as concentration of reactants decreases

  2. Rate of backward reaction increases as concentration of products increases

  3. At equilibrium, rate of forward reaction is the same as backward reaction
• Concentrations at Equilibrium


  • [R] = [P]
  • [R] > [P]
  • [R] < [P]
• Equilibrium Constant (K)


  A measure of the ratio of product concentrations to reactant concentrations at equilibrium
• Equilibrium Constant Expression


  1. K = [C]^m * [D]^n / ([A]^x * [B]^y)

  2. K = (P_C^m * P_D^n) / (P_A^x * P_B^y)
• Equilibrium Constant


  • Depends on the temperature of the reaction
  • Has no specific units
  • Cannot be zero
• The larger the equilibrium constant, the further the equilibrium lies toward the products
• Manipulating Equilibrium Constant


  1. When the reaction is reversed: K_new = 1/K_original

  2. When the balanced equation is multiplied by a factor of n: K_new = (K_original)^n
• Homogeneous Equilibria


  Equilibria involving only one phase
• Heterogeneous Equilibria


  Equilibria involving more than one phase
• Expressing K_c and K_p


  1. For K_c, only include aqueous species and species in gas state

  2. For K_p, only include species in gas state