Equilibria

• Who is the presenter of the video on equilibria?

  Chris Harrison
• What is the purpose of the video on equilibria?

  To provide a quick overview of equilibria
• What can viewers do with the PowerPoint mentioned in the video?

  Purchase and use it for revision
• What does the term "reversible reactions" refer to?

  Reactions that can proceed in both directions
• How is the forward and backward reaction represented in equilibria?

  With arrows like harpoons
• What happens to the concentration of reactants over time in a reversible reaction?

  It decreases as reactants are used up
• What occurs when equilibrium is reached in a reversible reaction?

  The rate of forward reaction equals backward reaction
• What is a dynamic equilibrium?

  When concentrations remain constant
• In what type of systems does equilibrium occur?

  Only in closed systems
• What does Le Chatelier's principle state?

  Equilibrium shifts to counteract changes
• What happens if the concentration of a reactant is increased?

  Equilibrium shifts to reduce that concentration
• How does increasing pressure affect equilibrium?

  It shifts to the side with fewer gas particles
• What is the effect of increasing temperature on equilibrium?

  It shifts in the endothermic direction
• What is the role of catalysts in equilibrium reactions?

  They speed up both forward and backward reactions
• What is the reaction for producing ethanol from ethene?

  Ethene reacts with water to form ethanol
• What is the compromise temperature used in the ethanol production reaction?

  300 degrees Celsius
• What does increasing pressure do in the ethanol production reaction?

  It shifts equilibrium to produce more ethanol
• What is the equilibrium constant denoted as?

  KC
• How is the KC expression formulated?

  Products divided by reactants in concentration
• How do you calculate the value of KC for a reaction?

  Use molar concentrations in the KC expression
• What is the significance of the molar values in the KC expression?

  They become powers in the expression
• What must be used in the KC expression?

  Concentration, not moles
• What is the KC expression for the reaction given?

  KC = [SO3]^2 / [SO2]^2[O2]
• How do you calculate the value of KC for the reaction?

  Substitute concentrations into the KC expression
• What is the concentration of SO3 used in the KC calculation?

  3.8 moles per dm³
• What is the concentration of SO2 used in the KC calculation?

  0.4 moles per dm³
• What is the concentration of O2 used in the KC calculation?

  0.2 moles per dm³
• What is the final step in calculating KC?

  Perform the calculation with substituted values
• What do square brackets indicate in a KC expression?

  Concentration of reactants and products
• Why must concentrations be used instead of moles in KC expressions?

  Because KC is based on concentration values
• How do you write the KC expression for a reaction?

  Products over reactants with powers
• What is the KC expression for the reaction involving $SO_2$, $O_2$, and $SO_3$?


  KC = $\frac{[SO_3]^2}{[SO_2]^2[O_2]}$
• How are units for KC determined?

  By analyzing the concentration units in the expression
• What does the acronym ICE stand for in equilibrium calculations?

  Initial, Change, Equilibrium
• How do you calculate the number of moles of $NO_2$ from its mass?


  Mass divided by molar mass
• What is the molar mass of $NO_2$?


  46 g/mol
• How do you find the number of moles of $O_2$ at equilibrium?


  Mass divided by molar mass
• What is the mass of $O_2$ found in the equilibrium mixture?


  6.8 grams
• What is the number of moles of $O_2$ at equilibrium?


  0.215 moles
• How do you determine the change in moles for $NO$?


  By using the molar ratio from the reaction