Reaction rates and Equilibrium

Cards (27)

  • Why does increased concentration increase rate of reaction?
    More likely for particles with high enough Ea to have successful collisions per second, resulting in higher likelihood of reaction occurring
  • Why does increased surface area increase rate of reaction?
    Increasing surface area increases the likelihood of successful collisions per second, which increases likelihood of reaction occurring
  • Why does increased temperature increase rate of reaction?
    The particles will have increased kinetic energy, therefore more particles will have the required activation energy
  • Why does increased pressure increase rate of reaction? ONLY FOR GASES
    The particles will be in a smaller volume, therefore more successful collisions with the necessary Ea will occur, therefore reaction rate will be increased
  • What is a catalyst?
    Increases reaction rate without being used up by offering alternative route with lower activation energy
  • Why is a catalyst used?
    -To provide a pathway with lower activation energy or provide a surface for the reactant to take place on
  • What is a homogenous catalyst?
    A catalyst in the same phase as the reactants
  • What is a heterogenous catalyst?
    A catalyst in a different phase as the reactants
  • What is beneficial about using a catalyst?
    It reduces temperature required to start non-spontaneous reactions
    -More economically viable than increasing temp/ pressure which uses more fuel
  • Maxwell-Boltzmann distribution

    Shows the distribution of energies that molecules of gas or liquid have at a particular temperature
  • Features of a Maxwell-Boltzmann distribution
    - No molecules have zero energy - the curve starts at the origin
    - The area under the curve is equal to the total number of molecules
    - There is no maximum energy for a molecule - the curve does not meet the x-axis at high energy
  • How does Boltzmann distribution change with temperature?
    Higher temperature - Probable speed point shifts right and lower down as more particles are more likely to have Ea
  • How does Boltzmann distribution change with catalysts?
    Graph itself does not change - Activation energy
  • What is dynamic equilibrium?
    Where the rate of the forward reaction and the rate of the backward reaction are equal in a closed system
  • What is important about the concentration of reactants and products in a closed system?
    They do not change
  • What is Le Chatelier's principle?
    When changes are made to a system, the system will oppose them
  • What happens when temperature is increased in a closed system?
    The reaction will shift in the endothermic direction
  • What happens when pressure is increased in a closed system?
    The side with less moles is favoured
  • What happens when concentration of product is increased?
    The reactant is favoured
  • How do catalysts act in dynamic equilibria?
    They increase the rate of reaction of both the forward and backward reaction equally, resulting in an unchanged position of equilibrium
  • What are compromise conditions?
    Conditions that maximise yield of product with the most economically viable conditions
  • What is Kc?
    The equilibrium constant
  • Kc = 1
    Equilibrium is in the middle
  • Kc < 1
    Equilibrium shifts left
  • Kc > 1
    Equilibrium shifts right
  • How is Kc calculated?
    Kc=[C]^c x [D]^d/[A]^a x [B]^b
  • What is the energy rate rule?
    Every 10 degree increase, the rate doubles