1. Integrated rate laws ln[A] = -kt + ln[A]0 rate = k[A]
1/[A] = kt + 1/[A]0
rate = k[A]2

2. Reaction mechanism reaction =  Elementary steps Molecularity
rate law
unimolecular
A  product
k[A]
bimolecular
A+ B  product
k[A][B]
termolecular
A+B+C  product
k[A][B][C]
A+A+A  product
k[A]3
chemical reaction
= sum of elementary steps
rate law
and stoichiometry

3. Reaction mechanism increase rate of reaction
2H2O2 (aq)  2H2O(l) + O2(g)
Gorxn =
[ 2(-237.9)]
- [2( )]
= kJ
spontaneous reaction
experimental rate law:
rate = k[H2O2]
[I-]
I- =
catalyst
increase rate of reaction
not consumed in the overall reaction
reactant in early elementary step
product in later elementary step

4. Reaction mechanism 2H2O2 (aq)  2H2O(l) + O2(g) rate = k[H2O2] [I-]
step 1
H2O2
+ I-
 H2O
+ OI- k2
step 2
H2O2 +
OI- 
H2O + O2
+I-
2H2O2 (aq) 
2H2O(l)
+ O2(g)
step 1
rate = k1
[H2O2]
[I-]

5. Reaction mechanism step 1 H2O2 + I-  H2O + OI- step 2k1
step 1
H2O2 + I-  H2O + OI- k2
step 2
H2O2 + OI-  H2O + O2 +I-
what about step 2 ?
assume k2
>> k1
step 1
rate determining step
I- catalyst
consumed in rate determining step
regenerated in later elementary step
OI-
intermediate
formed in early step,
consumed in later step

6. Rate determining step
on Labor Day weekend
“Big Mac” bridge

7. Reaction Mechanism H2(g) + I2(g)  2HI(g) rate = k [H2] [I2]
reaction faster in light
free radical
unpaired electron

8. Reaction Mechanism H2(g) + I2(g)  2HI(g) rate = k [H2] [I2]  I2 2I.
step 1 
forward rate
= kf [I2]
reverse rate =
kr [I.]2
equilibrium
kf[I2] =
kr[I.]2
Keq=
[I.]2
= kf
[I2] kr

9. Reaction Mechanism H2(g) + I2(g)  2HI(g) rate = k [H2] [I2] I2 2I. 
step 1
step 2
H2 +
2I.
2HI H2
+ I2 
2HI
need H2 in the rate determining step
from step 2
rate =
k [H2] [I.]2
I. =
intermediate

10. Reaction Mechanism H2(g) + I2(g)  2HI(g) rate = k [H2] [I2] I2 2I. 
step 1
step 2 H2 + 2I. 2HI
rate = k [H2] [I.]2
Keq =
[I.]2
= kf
[I2] kr
rate =
k [H2]
Keq [I2]
[I.]2 =
Keq [I2]
rate = k’ [H2] [I2]

11. Reaction Mechanism 2NO + O2  2NO2 rate = k[NO]2 step 1 2NO  N2O2 
overall reaction:
2NO + O2  2NO2
intermediates:
N2O2
relative rates of steps 1 and 2

12. 2NO + O2  2NO2
rate = k[NO]2
step 1
2NO  N2O2 
step 2
N2O2 + O2  2NO2