reversible reactions

• In a reversible reaction…

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

  exothermic ⇌ endothermic

  endothermic ⇌ exothermic

  ↳ The same amount of energy is transferred in each case (side).
• ammonium chloride ⇌ ammonia + hydrogen chloride

  ↳ white solid                  ↳ white gas

  hydrated copper sulfate ⇌ anhydrous copper sulfate + water

  ↳ blue                                          ↳ white

  (→ - endothermic

  ← - exothermic)
• Represented as: 

  A+B ⇌ C+D