Chemistry 2710 Spring 2000 Test 2

Name:

Aids allowed: calculator, one sheet of notes

Please write your answers in ink. If you have a graphing calculator, you can use it rather than hand drawing graphs. If you do use your calculator's graphing capabilities, explain in detail what you did (what graphs you drew, how you interpreted them, etc.). If you need to draw graphs by hand, graph paper is included at the end of this exam. Make sure to label your graphs with the question number.

1. In quiz 8, we calculated the Michaelis constant and for the reaction

   

   catalyzed by the enzyme carbonic anhydrase. The kinetic constants of the forward reaction were found to be and . Note that water has no detectable effect on the rate, being present in great excess. Accordingly, from a kinetic point of view, the reaction is just .

   In an initial rate study of the reverse reaction catalyzed by a 2.32nmol/L solution of the enzyme, the following data were obtained:

   

   1. Calculate and . [10 marks]

   2. Calculate the equilibrium constant for the reaction. From thermodynamics, we can calculate that at and 7. Is your answer in reasonable agreement with this value? [3 marks]

   3. Calculate and . [4 marks]

2. The decomposition of ozone to form oxygen occurs by the reaction

   

   where X can be any of a number of inert species present in the atmosphere (nitrogen, argon, etc.).

   1. Identify a particularly reactive species present in this reaction. Argue, based on the existence of the highly reactive species identified, that a particular approximation can be used in deriving the rate law. [3 marks]

   2. What is the overall reaction? [2 marks]

   3. Use an appropriate approximation to derive a rate law for this reaction. [10 marks]

      Note: I expect some degree of simplification in your answer.

   4. If you were studying this reaction in controled laboratory conditions, you could systematically vary the pressure. How does the order of the reaction with respect to vary with pressure? Focus particularly on the high- and low-pressure limits. What other changes in the empirical rate law would you observe as a function of pressure? [6 marks]
3. In a series of enzyme inhibition experiments, the following data were obtained:

   

   1. Are these data compatible with competitive inhibition? Explain briefly. [5 marks]

      Hint: It might be sensible to use a graphical method to address at least part of this issue.

   2. On the assumption that this is an instance of competitive inhibition, calculate , and . [7 marks]