Rates of Reaction

  1. Consider the reaction of H2 with ethyne to give ethane.

    2 H2 + C2H2 → C2H6
    Determine the rate law and rate constant for the reaction from the following data:

    initial concentration of H2initial concentration of ethynerate of formation of ethane
    0.10 M 0.10 M 1.0 x 10-4 M/min
    0.20 M 0.10 M 2.0 x 10-4 M/min
    0.10 M 0.20 M 1.0 x 10-4 M/min
  2. Carefully explain the difference between the reaction of methyl iodide and t-butyl chloride with hydroxide ion. Give the rate law for each, a mechanism, and a reaction profile.
  3. For the reaction:

    N2O4 → 2 NO2
    the following data were collected:

    N2O4 at startamount of NO2 after 1 min
    1.0 M 0.6 M
    0.5 M 0.3 M
    0.25 M 0.15 M
    1. Give the rate law for this reaction.
    2. Calculate the rate constant.
    3. When the reaction is started with 1.0 mole of N2O4 in a 1.0 L flask, how much N2O4 remains after 1 min?
    4. Calculate ΔH for this reaction.
    5. Postulate a mechanism for this reaction.
    6. Give a reaction profile for this mechanism and clearly label all parts of the profile.
    7. N2O4 has the following structural formula:
      structural formula

      where the nitrogens are attached to each other and the oxygens are attached only to a nitrogen. Write an electron-dot formula for this molecule and put in the formal charges.

    8. Is the electron-dot formula for N2O4 in g. above helpful in explaining your mechanism? Explain.
    9. Draw a picture showing the relative positions of all of the atoms in the transition state (if there are more than one in your mechanism, show each one).