rate equations & kp

• rate equations

  • how fast reactants are converted into products
  • depends on the concentrations of the reactants and a rate constant
  • the constants m and n show the order of reaction with respect to that species
  • total order of the reaction = m + n

  
• orders of reaction graph

  • zero order -> concentration of species has no impact on rate
  • rate = k

  
• orders of reaction graph

  • first order -> the concentration of the species and rate are directly proportional
  • rate = k[A]

  
• orders of reaction graph

  • second order -> rate is proportional to the concentration squared
  • rate = k[A]⌃2

  
• rate constant

  • rate constant for a reaction is constant when the temp is constant
• arrhenius equation

  
• rate determining step

  • not all stages occur at the same rate but the overall rate is determined by the slowest step of the reaction
  • the rate equation contains all the species involved in the stages up to and including the rate determining step
  • in this step 2 is the rated determining step as a;; the reactants are given in the rate equation

  
• determining rate equations

  • determined experimentally by monitoring concentration of a reaction mixture over time
  • concentration time graph can be produced -> find the rate by drawing a tangent at t=0 -> drawn at this point as it is the only time when the exact conc is known
  • method repeated using varying concentrations to get a set of data for conc and ROR
  • graph of rate against conc can be plotted to determine the order of the reaction
• kp

  • equilibrium constant used for gaseous equilibria
  • all reactants and products must be in a gaseous state in order of kp to tbe calculated
• partial pressure

  • in a gaseous system each gas has a partial pressure which adds up to give the total system pressure
  • found by usingthe molar fraction -> use ICE table
  • measured in pascals mostly

  
• calculating kp