Chemistry 2000, Fall 96, Test 1

1. Suppose that a chemist measures the initial rate of disappearance of a reactant A as a function of concentration for the reaction :

   

   What is the experimental rate law? Also, calculate the rate constant. [10 marks]

2. Suppose that the amount of C in a sample can be accurately measured until its abundance has been reduced to 1% of the amount found in living organisms. How old a fossil can be dated with the carbon-14 technique? The half-life of C is 5730 years. [10 marks]
3. Write down the rate equations for the mechanism

   

   Classify all of the species as reactant, product, intermediate or catalyst. [10 marks]

4. A first-order rate constant is measured and found to be at C and at C. What are the activation energy and preexponential factor ( ) for this reaction? [10 marks]
5. The third-order equation is

   

   1. Define half-life. [2 marks]
   2. Derive an expression for the half-life of a third-order reaction in terms of the initial concentration of the reactant and the rate constant. [8 marks]
   3. For [A] in mol/L and time in s, what are the units of a third-order rate constant? Hint: This is just a matter of unit analysis. [2 marks]
   4. You are told that a certain reaction obeys third-order kinetics. Explain how you would use this equation along with data giving [A] as a function of time to obtain the rate constant. [8 marks]