Mechanisms                                                                                                   

For the mechanism

A+ B ß> C + B (k₁ forward reaction, k_-1 reverse)

C à P  (k₂)

The steady state approximation should be used for ______________

Using the steady state approximation, gives the expression

[C]=rate=     (expression in terms of k1,k2 and [A] and [B])

1. Graphed below are the concentrations of A, B, and C as a function of time.  In this case k1=0.1 and k2=0.2.  

Decide whether each of the following 4 mechanisms could match what is observed in the graph.  You must explain your decision for each case (does it match or not and WHY!)

3.  We went through Michaelis-Menten kinetics very quickly in class.  Starting with the slide labled Michaelis-Menten kinetics (2), show a complete derivation of the equation

and then show how this equation can be rearranged to give a linear form used in the lineweaver Burke plot. 

(note:  this is how you should be studying for all mechanisms I show, working through each step) 

4. A possible mechanism for the decomposition of ozone in the reaction    2O₃ (g) à 3 O₂ (g) is: 

O₃à O₂ + O   ka

O₂+ O à O₃  ka’

O+ O₃ à O₂ + O₂   kb

a) The intermediate in this reaction is _____________________

b) Write an expression for d[I]/dt   where I is the compound you have identified as an intermediate 

c)  Use the steady state approximation  for d[I]/dt 

d)  Write an expression for   d[O₃]/dt 

e)  Show that by combining c) and d)  you can get the expression

d[O₃]/dt=-2kakb[O₃]²/(ka’[O₂]+kb[O₃]) 

f) What order would the reaction be if kb>> ka’? 

5.  Look at the diagrams given below.  In which case(s ) would the steady state be valid? Why?