Kinetics

• What is the rate of reaction?

  The change in concentration with unit time
• How would we find the rate of change of a reactant at a particular instant?

  Draw a tangent to the curve at that particular instant and find its gradient (make it as long as possible)
• What is the unit for reaction rate?

  mol dm$^{-3}$s$^{-1}$
• if Y is in second order and X is in first order, what is the rate equation?

  rate = $\left[X\right]\left[Y\right]^2$
• What affects k?


  Temperature
• What is the order of the reaction?

  The power to which the concentration of that species is raised in the rate expression.
• What is the overall order of the reaction?

  The sum of the powers.
• How would we say what the order of the reaction is with one reactant?

  The order is....in respect to [X]
• What is the overall and individual orders of this reaction:

  rate = [X][Y]$^2$


  • The overall order of this reaction is third order
  • It is first order with respect to X
  • And second order with respect to Y
• If a reactant does not appear in the rate equation, what order can we say it is in?

  Zero order
• What are the units of k in a first order reaction?

  s$^{-1}$
• On a concentration-time graph, if the gradient is a straight line what is the order of reaction?


  Zero order
• On a concentration-time graph, if the graph is a sloping straight line through the origin, what order is the reaction?


  First
• On a concentration-time graph, if the gradient is sloping and not straight, what is the order of reaction?


  More than one
• The larger the value of k...


  The faster the reaction
• What is the rearranged form of the arrhenius equation?

  $\ln k=$$\ln A-\frac{Ea}{RT}$
• What is the arrhenius equation?

  $k\ =$$A\ e^{-\frac{Ea}{RT}}$
• What does the gradient on a $\ln k\ \frac{1}{T}$graph equal to?


  $-\frac{E_a}{R}$
• What are the units we calculate activation energy in from a $\ln k\ \frac{1}{T}$graph? What should they be in?


  J mol$^{-1}$, need to be in KJ mol$^{-1}$
• What does $e^{-\frac{E_a}{RT}}$mean?


  The fraction of molecules with energy greater than the activation energy.
• Define rate constant.


   a measure of the speed of a chemical reaction
• What is temperature?


  A measure of the average kinetic energy of particles in a substance.
• What is the rate-determining step?

  The slowest step in a chemical reaction that determines the overall rate of the reaction.
• What steps affect the rate of the reaction?

  Any steps before the rate-determining step