Sub-topic #1: Equilibrium Shifting

• Equilibrium – condition during a reversible chemical

  reaction in which no net change in the amounts of

  reactants and products occurs.
• Reversible Chemical Reaction – where the products,

  as soon as they are performed, react to produce the

  original reactants.
• The position of equilibrium describes the relative

  amounts of reactants and products that remain at the end of a chemical reaction.
• The equilibrium position of a reaction may shift if

  an external stress is applied.
• Stress – may be in the form of a change in

  temperature, pressure, or the concentration of one

  of the reactants or products.
• The response of a reaction at equilibrium to changes in conditions is summarized by Le Chatelier’s Principle.
• Le Chatelier’s Principle – a system perturbed from

  equilibrium shifts its equilibrium position to relieve

  the applied stress.
• Meaning, when something causes a change (stress) in a system that is in equilibrium, the system will adjust itself to reduce or counteract that change and try to get back to balance.
• Example: If you add more reactant to a reaction at

  equilibrium, the system will shift to use up some of

  that extra reactant by making more product.
• If you increase the temperature or pressure, the system will shift in a way that reduces the effect of that change.