Lecture 02

• What is the concept of rate of reaction?

  Speed at which reactants convert to products
• What are reaction orders?

  Exponents in the rate law equation
• How can reaction orders be determined?

  From experimental data analysis
• How can reaction rate constants be calculated?

  Using experimental data
• How is half-life calculated for reactions?

  Graphically and numerically
• What is the rate equation for zero-order reactions?

  rate = k
• What does the gradient of the plot [A] against time represent in zero-order reactions?

  It represents the rate constant k
• What is the integrated rate law for zero-order reactions?

  [A]t = [A]0 - kt
• What does a plot of [A] versus time look like for zero-order reactions?

  It gives a straight line

  
• How does the half-life of a zero-order reaction change with concentration?

  It decreases as concentration decreases
• What is the definition of half-life in reactions?

  Time for concentration to decrease by half
• How do you calculate half-life graphically for zero-order reactions?

  1. Define initial concentration from graph
  2. Divide that concentration by 2
  3. Draw perpendicular line to y-axis
  4. Draw parallel line to x-axis to find time
• What is the integrated rate law for zero-order reactions used to calculate half-life?

  [A]t = [A]0 - kt
• What is the relationship between half-life and initial concentration in zero-order reactions?

  Half-life is proportional to initial concentration
• What is the rate equation for first-order reactions?

  rate = k[A]
• What does a plot of ln([A]) versus time look like for first-order reactions?

  It gives a straight line
• How is the rate of reaction for first-order reactions determined?

  By the change in concentration over time
• What is the rate equation for second-order reactions?

  rate = k[A]^2
• How does a plot of 1/[A] versus time appear for second-order reactions?

  It gives a straight line
• What is the relationship between the rate of reaction and concentration in second-order reactions?

  Rate is proportional to the square of concentration
• What is the integrated rate law for second-order reactions?

  1/[A]t = 1/[A]0 + kt
• What is the first step to determine the order of a reaction?

  Check for zero-order reaction
• How can the order of a reaction be confirmed?

  By plotting concentration versus time
• What is the half-life of a reaction?

  Time to decrease concentration by half
• How do you calculate half-life graphically for first-order reactions?

  1. Define initial concentration from graph
  2. Divide that concentration by 2
  3. Draw perpendicular line to y-axis
  4. Draw parallel line to x-axis to find time
• What is the integrated rate law for first-order reactions used to calculate half-life?

  ln([A]t) = ln([A]0) - kt
• What is the half-life formula for second-order reactions?

  t1/2 = 1/[A]0k
• How does the half-life of a second-order reaction change with concentration?

  It increases as concentration decreases
• What are the characteristics of zero-order reactions?

  • Rate is independent of reactant concentration
  • Plot of [reactant] vs. time is linear
  • Rate constant has units of concentration x time^-1
  • Half-life is proportional to [A]0/2k
• What are the characteristics of first-order reactions?

  • Rate is proportional to reactant concentration
  • Plot of ln([reactant]) vs. time is linear
  • Rate constant has units of time^-1
  • Half-life is constant and independent of concentration
• What are the characteristics of second-order reactions?

  • Rate is proportional to the square of reactant concentration
  • Plot of 1/[reactant] vs. time is linear
  • Rate constant has units of time^-1 x concentration^-1
  • Half-life is inversely proportional to reactant concentration
• What is the order of the reaction for the oxidation of stearic acid?

  First order
• What is the rate constant for the oxidation of stearic acid?

  0.053 min^-1
• How can the half-life of the oxidation of stearic acid be calculated?

  Analytically and graphically
• What is the slope of the line for the oxidation of stearic acid?

  -0.0538
• What is the y-intercept of the line for the oxidation of stearic acid?

  4.6653