equilibria

• What does the term "reversible reactions" refer to in the context of equilibria?

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

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

  The concentration of reactants decreases as they are used up
• What is dynamic equilibrium?

  It is when the rate of the forward reaction equals the rate of the backward reaction
• What is the key difference between concentration and the amount of reactants and products?

  Concentration refers to the amount of substance per unit volume, while amount refers to the total quantity
• In what type of systems does equilibrium occur?

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

  If a reaction at equilibrium is subjected to a change in pressure, temperature, or concentration, the position of equilibrium will shift to counteract that change
• What happens to equilibrium if the concentration of a reactant is increased?

  The equilibrium will shift to the right to reduce the concentration of that reactant
• What is the effect of increasing pressure on equilibrium?

  The equilibrium will shift to the side with fewer gas particles
• How does temperature affect equilibrium in an exothermic reaction?

  Increasing the temperature shifts the equilibrium to the left, while decreasing it shifts to the right
• What is the role of catalysts in equilibrium reactions?

  Catalysts speed up both the forward and backward reactions but do not affect the position of equilibrium
• 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 production of ethanol?

  300 degrees Celsius
• What does the equilibrium constant (Kc) represent?

  Kc gives a value to an equilibrium reaction based on the molar concentrations of reactants and products
• How do you write the Kc expression for a reaction?

  Products divided by reactants, with the molar values as powers
• What is the Kc expression for the reaction where $2A +$$B \rightleftharpoons 3C +$$D$?


  $K_c =$$\frac{[C]^3[D]}{[A]^2[B]}$
• Given the concentrations of $[SO_2] =$$0.4 \text{ mol/dm}^3$, $[O_2] =$$0.2 \text{ mol/dm}^3$, and $[SO_3] =$$3.8 \text{ mol/dm}^3$, what is the Kc expression?


  $K_c =$$\frac{[SO_3]^2}{[SO_2]^2[O_2]}$
• How do you calculate the value of Kc for the reaction given the concentrations?

  Substitute the concentrations into the Kc expression and calculate
• What is the significance of square brackets in the Kc expression?

  Square brackets indicate concentration
• Why is it important to use concentration in the Kc expression?

  Because Kc is based on the molar concentration of reactants and products
• How does the change in temperature affect the equilibrium position in an endothermic reaction?

  Increasing temperature shifts the equilibrium to the right, while decreasing it shifts to the left
• What are the compromises made in the production of ethanol regarding temperature and pressure?

  Low temperature for yield vs. high temperature for reaction rate; high pressure for yield vs. cost and safety
• What is the effect of increasing the concentration of ammonia on the equilibrium?

  The equilibrium will shift to the left to use up the increased ammonia
• What happens to the equilibrium when the pressure is decreased?

  The equilibrium will shift to the side with more gas particles
• What is the relationship between the amount of gas particles and pressure in equilibrium reactions?

  Increasing pressure favors the side with fewer gas particles
• How does a catalyst affect the time taken to reach equilibrium?

  A catalyst speeds up the rate at which equilibrium is established
• What is the significance of the enthalpy value in relation to temperature changes in equilibrium?

  The enthalpy value determines the direction of the shift when temperature changes
• What is the effect of decreasing temperature on an exothermic reaction at equilibrium?

  Decreasing temperature shifts the equilibrium to the right, producing more products
• What is the effect of increasing the concentration of hydrogen on the equilibrium of the reaction?

  The equilibrium will shift to the right to use up the increased hydrogen
• What happens to the equilibrium when the concentration of a product is decreased?

  The equilibrium will shift to the right to produce more of that product
• How does the concentration of reactants and products affect the position of equilibrium?

  Changes in concentration will shift the equilibrium to counteract the change
• What is the relationship between the number of gas particles and the pressure in equilibrium reactions?

  Increasing pressure favors the side with fewer gas particles
• What is the significance of the equilibrium constant Kc?

  Kc quantifies the ratio of concentrations of products to reactants at equilibrium
• How do you determine the Kc value from a reaction?

  By substituting the concentrations into the Kc expression
• What is the effect of a catalyst on the yield of a reaction at equilibrium?

  A catalyst does not affect the yield of the reaction
• What is the relationship between the rate of reaction and the position of equilibrium?

  The rate of reaction does not affect the position of equilibrium
• What is the effect of increasing the concentration of a product on the equilibrium?

  The equilibrium will shift to the left to use up the increased product
• How does the equilibrium position change when the concentration of a reactant is decreased?

  The equilibrium will shift to the left to produce more reactants
• What is the significance of the equilibrium constant in predicting the direction of a reaction?

  The equilibrium constant helps predict whether the reaction will favor products or reactants
• What is the effect of increasing the pressure on the equilibrium position?

  Increasing pressure shifts the equilibrium to the side with fewer gas particles