Reversible Reactions

• Reversible reactions


  Reactions that go both ways
• Reversible reaction


  1. Reactants (A and B) form products (C and D)

  2. Products (C and D) react to form reactants (A and B) again
• Reversible reaction


  • Indicated by the symbol
• Forward reaction


  Reaction of A and B
• Backward reaction


  Reaction of C and D
• Reaching equilibrium in a reversible reaction


  1. Reactant concentrations fall, forward reaction slows

  2. Product concentrations increase, backward reaction speeds up

  3. Forward and backward reactions reach the same rate
• Equilibrium


  Amounts of products and reactants are not changing anymore
• Equilibrium is only reached in a closed system where nothing can escape or enter
• More products than reactants at equilibrium

  Reaction is going in the forwards direction
• More reactants than products at equilibrium


  Reaction is going in the backwards direction
• Changing conditions (temperature, pressure, concentration)

  Can change the direction of the reversible reaction
• Ammonium chloride decomposition and reformation


  1. Ammonium chloride breaks down to form ammonia and hydrogen chloride

  2. Hydrogen chloride can react with ammonia to reform ammonium chloride
• Heating the ammonium chloride reaction


  Drives the reaction in the forwards direction
• Cooling the ammonium chloride reaction


  Drives the reaction in the backwards direction
• Endothermic reaction


  Reaction that takes in heat
• Exothermic reaction


  Reaction that gives out heat
• The amount of energy taken in by an endothermic reaction is the same as the amount given out by the corresponding exothermic reaction
• Anhydrous


  Without water
• Hydrated


  With water
• Anhydrous copper sulfate and hydrated copper sulfate


  • Anhydrous copper sulfate is white
  • Hydrated copper sulfate is blue