energy changes

• the products of the reaction can react to produce the original reactants
• the direction of reversible reactions can be changed by changing the conditions

  i.e. heating or cooling
• example of reversible reaction:

  ammonium chloride <--> ammonia + hydrogen chloride

  left = cool, right = heat
• if a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction, and the same amount of energy would be transferred in each case
• energy in reversible reaction example:

  hydrated copper sulfate (blue) <--> anhydrous copper sulfate (white) + water

  forwards = endothermic, backwards = exothermic
• When a reversible reaction occurs in apparatus which prevents the escape of reactants and products (i.e. container)

  equilibrium is reached when the forward and reverse reactions occur at exactly the same rate