topic 10 equilibrium

Cards (14)

  • why are catalyst used in industrial processes?
    • catalyst increases the rate at which the reaction moves towards equilibrium.
    • decreases the time a reaction takes to arrive at a particular yield of a product.
    • provides an alternate reaction pathway, promoting a lower activation energy.
    • & allows milder conditions to be used, therefore lowering the cost.
  • effect of increased temp. on equilibrium
    • if temp is increased,
    • equilibrium will shift to oppose this,
    • & move in the endothermic, backwards reaction,
    • to try & decrease the temp by absorbing heat energy.
    • the position of equilibrium will shift towards the left,
    • giving a lower yield of the substance.
  • effect of decreased temp on equilibrium:
    • if temp is decreased,
    • equilibrium will shift to oppose this,
    • & move in the exothermic, forward direction,
    • to try & increase the temp by giving out heat energy.
    • the position of equilibrium will shift towards the right,
    • giving higher yield of the substance.
  • effect of increased pressure on equilibrium:
    • if pressure is increased,
    • equilibrium will shift to oppose this,
    • & move towards the side with fewer moles of gas to try to reduce the pressure.
    • the position of equilibrium will shift towards the *right/left
    • (describe the moles on both sides shown)
    • giving higher yield of a substance
  • Kc formula
    Kc = [C]p [D]q / [A]m [B]n
    A, B, C, D = chemical formula
    m, n, p, q = stoichiometric balance number (moles)
  • effect of decreased pressure on equilibrium:
    • if the pressure is decreased,
    • the equilibrium will shift to oppose this,
    • & move towards the side with more moles,
    • to try & increase the pressure,
    • the position of equilibrium will shift towards the fewer moles because there are,
    • (describe the moles shown)
    • giving lower yield of a substance.
    • in all cases, high pressure leads to too high energy costs,
    • for pumps to produce pressure,
    • & too high equipment costs to have certain apparatus,
    • that can withstand high pressures
  • larger the Kc
    greater amount of products
  • smaller Kc
    the equilibrium favours the reactants
  • what one thing is Kc only affected by
    temp
  • Haber Process: N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
    • The reaction is exothermic in the forward direction
    • Therefore, an increase in temperature may increase the rate of reaction but it will decrease the overall yield as the equilibrium shifts to the left.
    • An increase in pressure will increase the yield
    • This is because there are 4 moles of reactant compared to only 2 moles of product.
  • The value of Kc indicates the position of equilibrium:
    Kc = 1 - the position of equilibrium is halfway between the reactants and products.
    Kc < 1 - the position of equilibrium lies towards the left-hand side, i.e. the reactants.
    Kc > 1 - the position of equilibrium lies towards the right-hand side, i.e. the products.
  • Effect of an increase in pressure on the rate of reaction:
    • Rate increases because there are more molecules per unit volume; [1 mark]
    • So there is an increase in the frequency of collisions between reacting molecules; [1 mark]
  • Heterogeneous means:
    • The catalyst is in a different phase of state to the reactants
    A catalyst has no effect on the yield of the products in the reaction because:
    • A catalyst increases the rate of the forward and backward reactions