Rate Equations

• 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 does a zero-order reaction imply about the concentration of a species?

  The concentration has no impact on the rate.

  
• How is a first-order reaction characterized?

  The concentration of the species and rate are directly proportional.
• What happens to the rate in a second-order reaction when the concentration is doubled?

  The rate increases by four.
• What is the rate constant (k) in a reaction?

  It is constant when the reaction temperature is constant.
• How can the rate constant be found?

  By rearranging the rate equation for that reaction.
• What affects the units of the rate constant (k)?

  They vary depending on the number of species and their orders of reaction.
• What does the Arrhenius Equation show?

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

  
• How can the logged form of the Arrhenius Equation be represented graphically?

  As 'y = mx + c' with a graph of lnk against 1/T.

  
• What does the gradient of the graph of lnk against 1/T represent?

  The gradient is negative and constant.
• What is the y-intercept of the graph of lnk against 1/T?

  It is lnA.
• 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.

  
• What is the method for determining rate equations experimentally?

  By monitoring the concentration of a reaction mixture over time.
• What can be used to find the rate from a concentration-time graph?

  A tangent can be drawn to the curve at t=0.
• Why is the tangent drawn at t=0 on the concentration-time graph?

  It is the only time in the reaction where the exact concentration is known.

  
• What is done after obtaining the rate from the tangent at t=0?

  This 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 can be plotted.