6. equilibria

• What does the term "reversible reactions" refer to?

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

  With arrows resembling 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 the forward reaction equals the backward reaction
• What is the term for the state when the concentration of reactants and products remains constant?

  Dynamic equilibrium
• In what type of systems does equilibrium occur?

  Closed systems
• What does Le Chatelier's principle state?

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

  It shifts to the right to use it up
• How does increasing pressure affect equilibrium?

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

  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 and water?

  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 the right
• What is the equilibrium constant denoted as?

  KC
• How is the KC expression formulated?

  Products divided by reactants in concentration
• If the concentration of SO2 is 0.4 moles per dm³, what is its role in the KC expression?

  It is squared in the expression
• What is the molar concentration unit used in the KC expression?

  Moles per dm³
• Why must concentrations be used instead of moles in the KC expression?

  Because KC is based on molar concentrations
• How do you calculate the value of KC for a reaction?

  By substituting concentrations into the KC expression
• What is the significance of the powers in the KC expression?

  They represent the molar coefficients from the balanced equation
• 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 unit for KC in the example?

  moles per dm3
• What does the ICE table represent in equilibrium calculations?

  Initial, Change, and Equilibrium concentrations
• How do you calculate moles from mass and molar mass?

  Moles = mass / molar mass
• How do you find concentrations from moles and volume?

  Concentration = moles / volume
• What factors affect the value of KC?

  Temperature, concentration, and catalysts
• How does temperature affect KC?

  Changes in temperature alter KC
• What happens to KC if the equilibrium shifts to the right?

  KC increases
• What happens to KC if the equilibrium shifts to the left?

  KC decreases
• How do catalysts affect KC?

  Catalysts do not affect KC
• What is the process to calculate KC from equilibrium concentrations?

  1. Write the balanced chemical equation.
  2. Set up the KC expression.
  3. Substitute equilibrium concentrations into the expression.
  4. Calculate KC.
• How do you determine equilibrium concentrations using KC?

  1. Write the KC expression.
  2. Rearrange to solve for unknown concentrations.
  3. Substitute known values into the rearranged expression.
  4. Calculate the unknown concentrations.
• What are the effects of temperature changes on equilibrium?

  • Increasing temperature shifts equilibrium left (KC decreases).
  • Decreasing temperature shifts equilibrium right (KC increases).
• What is the significance of the ICE table in equilibrium problems?

  • Helps track initial, change, and equilibrium concentrations.
  • Facilitates calculations of equilibrium concentrations.
• What is the relationship between KC and concentration changes?

  • KC remains unchanged by concentration changes.
  • Concentration changes affect equilibrium position, not KC.
• What is the role of catalysts in equilibrium reactions?

  • Speed up the rate of reaching equilibrium.
  • Do not change the position or value of KC.