Static and Dynamic Equilibrium

• Dynamic equilibrium


  When the forward and reverse reactions happen at the same rate (reversible reaction), creating reactants and products
• Dynamic equilibrium


  • The forward and reverse reaction rates happen at the same time (equal)
• Equilibrium


  • Reached in a closed system
  • Involves a reversible reaction
• At equilibrium


  • Rate of forward reaction = rate of reverse reaction
  • Concentrations of the reactants and products stay the same
  • Macroscopic properties are constant
• State of equilibrium


  • Rate of reaction = rate of reverse reaction
• Forward reaction rate


  Decreases as more products are produced
• Reverse reaction rate


  Increases as more reactants are produced
• Dynamic equilibrium


  • Equilibrium is dynamic not static
  • Continuous interchange between reactants and products
  • Same rate as products change to reactants, and reactants to products
  • Macroscopic consistency - all observable properties e.g. colour
• Dynamic equilibrium


  • Must happen in a closed system - can only exchange energy with surroundings, but not matter e.g. precipitate
  • Can be reached from either direction
• At equilibrium


  • There is a mixture of reactants and products
  • Concentrations of reactants and products do not have to be equal
• Experiment to explain dynamic equilibrium

  1. Two measuring cylinders full of water

  2. The concentrations of reactants and products stay the same

  3. The forward and reverse reactions are constantly occurring causing the equilibrium to constant change

  4. Forward reaction = reverse reaction

  5. No water should be lost (closed system) to allow equilibrium to be reached
• Graphing equilibrium


  • Graphs are used to show the rates of reaction or the concentrations over time
  • Forward reaction is initially high
  • Reverse reaction is initially 0
  • Forward reaction will decrease quickly at the start then slow down
  • Reverse reaction will increase quickly at the start then slow down
  • The reactions will then be equal, reaching equilibrium
• Dynamic equilibrium

  • A closed system
  • Reactants and products are present, but one reactant may have been used up
  • Forward and reverse rates are 0
  • E.g. magnesium is being combusted in a closed container with excess oxygen