Equilibrium Reactions

• What is an open system?


  A reaction vessel that has no lid, meaning reactants and products are lost to the atmosphere.
• When it is an open system?


  The concentration of reactants decrease and products do not increase as they are lost to the at atmosphere. The reaction will continue to create more products until all reactants are gone, a complete reaction.
• What is a closed system?


  A reaction vessel that is closed off, or has a lid, meaning that no reactants or products can escape.
• What is an equilibrium system?


  If a reaction has enough energy to overcome the activation energy of both the forward and reverse reaction, then it will proceed forward and reverse. At any one time there will be a mix of reactants and products.
• What is a dynamic equilibrium reaction?


  A reaction is dynamic if it is incomplete, the bonds are being broken and reformed constantly, and the rates of forward and reverse reactions are equal.
• How do you measure equilibrium?


  By colour changes, or for acids/bases their pH changes.
• What is Le Chatelier's Principle


  If an equilibrium system is subjected to change, the system will adjust itself to partially oppose the effect of the change.
• If product or reactant is added how does the system react?


  The system partially opposes this change by moving to decrease this concentration.
• If product or reaction is removed how does the system react?

  The system will partially oppose the change by moving to increase this concentration.
• What happens when the pressure of a system is increased?


  The reaction partially opposes the change by moving to decrease the pressure, favouring the side with the least moles.
• What happens when the pressure of a system is decreased?


  The system partially opposes this change by moving to increase the pressure. This favours the side of the reaction with more moles.
• What happens to a system that was diluted?

  The concentration of particles in an aqueous solution can be decreased by diluting the system with water. Therefore double the volume is half the concentration.
• What happens to an endothermic reactions if the temperature increases?


  Energy is a reactant so if temperature is increased, the system partially opposes the change and creates more products.
• What happens to an exothermic reaction if the temperature is decreased?

  Energy is a product so if temperature is decreased, the system partially opposes the change and creates more reactants.
• How does a catalyst affect an equilibrium system?


  No impact on the equilibrium position but increases the rate of when equilibrium is reached.
• What is the Equilibrium Law Expression?


  Is used to determine relationship between the concentration of reactants and products, called the equilibrium constant (Kc).
• Equilibrium Law: General Expression?


  aA +bB -> cC + dD
• What is the Equilibrium Expression?


  Kc = [C]^c * [D]^d / [A]^a * [B]^b
• What are homogenous components?


  Reactants in the same state.
• Equilibrium expression only contains the homogenous componets.
• If dealing with a heterogenous system, don't include solids or liquids in the equilibrium expression.
• What is the Equilibrium constant (Kc)?


  A numerical value that is calculated using the concentration of products and reactants present at equilibrium for a reaction. It is for a reaction at a certain temperature as temperature is the only factor that affects it.
• What do Kc values mean?


  Kc>10^4 (more products than reactants)

  Kc<10^-4 (more reactants than products)

  Anything in between means no significant difference.
• What is the reaction quotient?

  The reaction quotient (Q) is a measure of the relative concentrations of reactants and products at any point during a chemical reaction.
• What does RICE stand for?


  R atio

  I nitial conc.

  C hange that occurs

  E quilibrium concentration