Chemical equilibrium

• What does dynamic equilibrium mean?

  Rates of forward and reverse reactions equal
• What occurs in a dynamic equilibrium?

  Concentrations of reactants and products remain constant
• What factors can alter the position of equilibrium?

  Concentration, pressure, and temperature
• What is Le Chatelier’s principle?

  • If a system at equilibrium is disturbed,
  • The equilibrium shifts to reduce the disturbance.
• What happens to equilibrium when temperature increases in an endothermic reaction?

  Equilibrium position shifts to the right
• In the reaction CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g), what effect does increasing pressure have?

  Equilibrium position shifts to the left
• Why might an industrial chemist use high pressure in hydrogen production?


  Increases collision frequency, speeding up reaction
• What effect does a catalyst have on the position of equilibrium?

  No effect on equilibrium position
• What conditions affect the value of Kc?

  Concentration, pressure, and temperature
• What is the expression for Kc for the reaction 2[A] + 3[B] + [C] ⇌ [D] + 4[E]?

  Kc = $\frac{[D][E]^4}{[A]^2[B]^3[C]}$

  
• What are the units for Kc?

  mol$^{-1}$ dm$^{-3}$
• For what type of system is Kc relevant?

  Homogeneous systems in equilibrium
• What does Kc being greater than 1 suggest?

  Equilibrium shifts to the right
• What happens to Kc when the temperature decreases in an endothermic reaction?

  Kc decreases
• What effect does increasing temperature have on Kc in an endothermic reaction?

  Kc increases
• What effect does decreasing temperature have on Kc in an exothermic reaction?

  Kc increases
• What happens to Kc when the temperature increases in an exothermic reaction?

  Kc decreases