Rates

• What does the rate of a reaction indicate?


  It shows how fast reactants are converted into products.
• What factors does the rate of a reaction depend on?


  It depends on the concentrations of the reactants and a rate constant.
• What do the constants m and n represent in a rate equation?


  They show the order of the reaction with respect to that species.
• How can the total order of a reaction be found?


  It can be found as the sum of the separate orders.
• What are the orders of reaction and their effects?


  • Zero Order: No impact on rate; Rate = k
  • First Order: Directly proportional; Doubling concentration doubles the rate; Rate = k[A]
  • Second Order: Proportional to concentration squared; Doubling concentration increases rate by four; Rate = k[A]^2
• What is the rate equation for a zero-order reaction?


  Rate = k
• How does the rate change in a first-order reaction when the concentration is doubled?


  The rate also doubles.
• What happens to the rate in a second-order reaction when the concentration is doubled?


  The rate increases by four times.
• What is the relationship between the rate constant (k) and temperature?


  The rate constant is constant when the reaction temperature is constant.
• How can the rate constant (k) be found?


  By rearranging the rate equation for that reaction.
• What does the Arrhenius Equation show?


  It shows how the rate constant k and temperature are related exponentially.

  
• What is the logged form of the Arrhenius Equation used for?


  To show the relationship graphically in the form 'y = mx + c'.
• What does the gradient of the graph of lnk against 1/T represent?


  The gradient is negative and constant.
• What determines the overall rate of a reaction?


  The overall rate is determined by the slowest step of the reaction.
• How can the rate determining step be identified?


  By looking at which steps include the species in the rate equation.
• In a reaction sequence, how can you determine which step is the rate determining step?


  Identify the step that includes all the reactants in the rate equation.
• How can rate equations be determined experimentally?


  By monitoring the concentration of a reaction mixture over time.
• What is the purpose of drawing a tangent to the concentration-time graph at t=0?


  To find the rate at the exact concentration known at that time.
• What is done after obtaining the rate from the concentration-time graph?


  The method is repeated at varying concentrations to gather data.
• What can be plotted to determine the order of reaction?


  A graph of rate against concentration.