Reversible reactions and dynamic equilibrium

• What are reversible reactions?

  Reactions that can proceed in both directions
• What does the term equilibrium mean in chemistry?

  State where forward and backward reactions equalize
• What symbol indicates a one-way reaction?

  Arrow pointing to the right
• What does a double arrow in a reaction signify?

  That the reaction is reversible
• What is the forward reaction in the example given?

  Ammonium chloride breaks down into ammonia and hydrogen chloride
• What is the backward reaction in the example given?

  Ammonia and hydrogen chloride combine to reform ammonium chloride
• How do the rates of forward and backward reactions change over time?

  Forward slows down, backward speeds up
• What happens when the reaction reaches equilibrium?

  Rates of forward and backward reactions equalize
• What does it mean when concentrations are constant at equilibrium?

  Reactants and products are still reacting
• Can the concentrations of reactants and products be equal at equilibrium?

  No, they can be different
• What does it mean if the equilibrium lies to the right?

  There are more products than reactants
• What does it mean if the equilibrium lies to the left?

  There are more reactants than products
• How can the position of equilibrium change?

  By altering conditions like temperature
• What happens when heat is added to a reaction?

  It encourages the forward reaction
• What happens when the reaction is cooled?

  It pushes the equilibrium to the left
• What is required for equilibrium to be reached in a reversible reaction?

  A closed system where nothing escapes
• What is the relationship between exothermic and endothermic reactions in reversible reactions?

  One is exothermic, the other is endothermic
• What does hydrated mean?

  Water is present
• What does anhydrous mean?

  No water is present
• What happens when hydrated copper sulfate is heated?

  It drives the reaction to form anhydrous copper sulfate
• What happens when heat is removed from anhydrous copper sulfate?

  It reforms hydrated copper sulfate
• What is released when the backward reaction occurs in the copper sulfate example?

  Energy absorbed in the forward reaction
• What are the key points about reversible reactions?

  • Indicated by a double arrow
  • Can proceed in both forward and backward directions
  • One direction is exothermic, the other endothermic
  • Equilibrium is reached when rates are equal
  • Concentrations remain constant at equilibrium
  • Position of equilibrium can shift based on conditions
• What is the thermal decomposition of hydrated copper sulfate?

  It produces anhydrous copper sulfate and water
• What color are hydrated copper sulfate crystals?

  Blue
• What color is anhydrous copper sulfate?

  White
• What happens to the water in hydrated copper sulfate when heated?

  It evaporates off
• What is the effect of adding water to anhydrous copper sulfate?

  It drives the backward reaction
• What is the overall change in concentrations at equilibrium?

  There is no overall change
• How do the concepts of exothermic and endothermic relate to reversible reactions?

  One direction absorbs heat, the other releases it
• What is the significance of a closed system in reversible reactions?

  It allows equilibrium to be reached
• What happens to the position of equilibrium when more reactants are added?

  It shifts to the right
• What happens to the position of equilibrium when more products are added?

  It shifts to the left
• What is the effect of increasing pressure on gaseous reactions at equilibrium?

  It shifts towards the side with fewer moles
• What is the effect of decreasing pressure on gaseous reactions at equilibrium?

  It shifts towards the side with more moles
• What is the effect of adding a catalyst on equilibrium?

  It speeds up the rate but not the position