5.1 Rates, Equilibrium and pH

• What is the rate of reaction measured by?

  Change in concentration over time

  
• What are the units for the rate of reaction?

  mol dm^-3 s^-1
• What does the rate expression Rate = k[D] indicate?

  Rate is directly proportional to [D]
• What happens to the rate if the concentration of D is doubled?

  The rate also doubles
• What is the general form of the rate equation for the reaction A + B → C + D?

  Rate = k[A][B]
• How are rate equations determined?

  They are determined experimentally
• What does the order of a reactant indicate?

  Its effect on the rate of reaction
• What does an order of 0 mean for a reactant?

  Concentration change has no effect on rate

  
• What does an order of 1 mean for a reactant?

  Concentration is directly proportional to rate

  
• What does an order of 2 mean for a reactant?

  Rate is proportional to the square of concentration

  
• What is the overall order of reaction?

  Sum of the powers of reactants in rate equation
• What is the order of the reaction for 2N₂O₅ → 4NO + O?

  Order is 1 with respect to N₂O₅
• What happens to the rate if the concentration of dinitrogen pentoxide is tripled?

  The rate also triples
• What is the overall order of the reaction BrO^- + 5Br^- + 6H⁺ → 3Br₂ + 3H₂O?

  Overall order is 3
• What is the effect on the rate if bromate concentration is doubled and bromide concentration is halved?

  No overall effect on the rate
• How do you determine the order with respect to a reactant?

  By analyzing experimental data
• What is the rate equation for the reaction (CH₃)₂Br + OH^- → (CH₃)₂OH + Br^-?

  Rate = k[(CH₃)₂Br][OH^-]
• What is the rate constant (k) calculated from?

  Initial rates and rate equation
• How do you calculate the units for the rate constant (k)?

  By substituting values into the rate equation

  
• What is the characteristic of a zero-order reaction's concentration-time graph?

  It is a straight line decreasing over time

  
• What does the gradient of a zero-order reaction graph represent?

  The rate of reaction

  
• How does the concentration of reactants change in a first-order reaction?

  It decreases over time

  
• What is the shape of a second-order reaction's concentration-time graph?

  It is a steeper downward curve

  
• How does the half-life of a zero-order reaction change over time?

  Successive half-lives decrease

  
• What is the half-life of a first-order reaction?

  It remains constant throughout the reaction
• How does the half-life of a second-order reaction change over time?

  It increases with time
• What does a pH graph indicate about the reaction curve?

  It shows a steeper downward curve

  
• What can be deduced from the half-life of a reaction?

  The order of the reaction
• How does the half-life of a zero-order reaction change over time?

  Successive half-lives decrease with time

  
• What is the half-life behavior of a first-order reaction?

  It remains constant throughout the reaction
• How does the half-life of a second-order reaction behave?

  It increases with time
• What are the characteristics of zero, first, and second-order reactions regarding half-lives?

  • Zero-order: Successive half-lives decrease
  • First-order: Half-life remains constant
  • Second-order: Half-life increases with time

  
• In a zero-order reaction, how does the rate depend on the concentration of the reactant?

  The rate remains constant throughout

  
• What does the rate equation for a zero-order reaction look like?


  rate = k

  
• How does the rate of a first-order reaction change with concentration?

  It is directly proportional to concentration
• What is the rate equation for a first-order reaction?

  rate = k[A]

  
• How does the rate of a second-order reaction relate to concentration?

  It is proportional to the square of concentration

  
• What is the rate equation for a second-order reaction?

  rate = k[A]^2

  
• What should you consider when calculating the rate constant, k?

  Use both graph and tabulated data

  
• What does the initial rates method measure?

  The rate at the very start of the reaction