Reversible reactions and equilibrium

•  the reversible reaction symbol is the double arrow
• The symbol ⇌ has two half arrowheads, one pointing in each direction.
•  It is used in equations that show reversible reactions:

  • the forward reaction is the one that goes to the right
  • the backward reaction is the one that goes to the left
• Example

  
• Energy changes in reversible reactions

  If a reaction is exothermic in one direction, it will be endothermic in the other direction. The same amount of energy is transferred in both the forwards and reverse reaction.
• Example

  
• Dynamic equilibrium

  When a reversible reaction happens in a closed container, it reaches a dynamic equilibrium. At equilibrium:

  • the forward and backward reactions are still happening
  • the forward and backward reactions have the same rate of reaction
  • the concentrations of all the reacting substances remain constant
• Equilibrium = balanced