Rate equations

• rate of a reaction shows how fast reactants are converted into products
• rate of a reaction depends on the concentration of the reactions and a rate constant
• rate = k[A]m[B]n

  the constants m and n show the order of the reaction with respect to that species.

  the total order of reaction for this chemical reaction can be found as the sum of the separate orders
• zero order:

  The concentration of the species has no impact on rate

  shown graphically as a horizontal line

  Rate = k
• first order:

  the concentration of the species and rate are directly proportional

  doubling concentration doubles the rate

  rate = k[A]
• second order:

  the rate is proportional to the concentration squared

  doubling the concentration will increase the rate by 4

  rate k[A]2
• the rate constant for a reaction is constant when the reaction temperature is constant
• the Arrhenius equation:

  ln k = - (Ea/RT) + ln A
• overall rate is determined by the slowest step of the reaction, therefore the rat equation contains all the species involved in the stages up to and including the rate determining step
• rate equations can be determined experimentally y monitoring concentration of a reaction mixture over time. the concentration-time graph produced can be used to find the rate
• tangent is drawn at 0 as it is the only time in the reaction where the exact concentration is known. this method is then repeated at varying concentrations o plot a graph of rate against concentration to work out the order of the reaction