The Foundations of Chemistry

706 CHAPTER 16: Chemical Kinetics

*89.For most reactions that involve an enzyme, the rate of

product formation versus reactant concentration increases

as reactant concentration increases until a maximum value

is obtained, after which further increases do not yield in-

creased rates. Using a description like that in Figure 16-19,

describe how the reaction may be first order with respect

to substrate but the amount of enzyme can also be a deter-

mining factor.

*90.Using the mechanism and energy values shown in Figure

16-12, prepare Lewis formulas that illustrate the species

that are likely to be present at each of the peaks and troughs

in the graphical representation given in Figure 16-12.

(Hint:You may need to label some bonds as being weaker,

stretched, in the process of being formed, and so on.)

*91.The activation energy for the reaction

2HI(g)88nH 2 (g)
I 2 (g)

is 179 kJ/mol. Construct a diagram similar to Figure 16-10

for this reaction. (Hint:Calculate H^0 from values in

Appendix K. How does H^0 compare with E^0 for this

reaction?)

*92.The activation energy for the reaction between O 3 and NO

is 9.6 kJ/mol.

O 3 (g)
NO(g)88nNO 2 (g)
O 2 (g)

(a) Use the thermodynamic quantities in Appendix K to

calculate H^0 for this reaction. (b) Prepare an activation

energy plot similar to Figure 16-10 for this reaction. (Hint:

How does H^0 compare with E^0 for this reaction?)