In kinetics we describe rates of change
The rate of change can be proportional to some power of the
concentration:
n=0
(zero order)
n=1 (first order)
k = rate constant
n = order of kinetics:
1. n=0 (zero order kinetics)
Solve differential equation:
dC = 
= 
= 
C = 
k has unit conc./time
Half life:
At t = 
= 
= 
® In zero order kinetics the half life is not constant but depends on the concentration.
Example:
C0 = 100 mg/ml
k0 = 10 mg/ml/h
| t[h] | C[ mg/ml] |
| 0 | 100 |
| 1 | 90 |
| 2 | 80 |
| 3 | 70 |
| 4 | 60 |
| 5 | 50 |
| 6 | 40 |
2. First Order Kinetics n=1
= 
Solve differential equation:
= 
= 
k
has units 1/time
Half life t1/2 = 0.693/k = constant
C = 
First Order Kinetics
C0 = 100 mg/ml
k = 0.693 h-1
| t[h] | C[ mg/ml] |
| 0 | 100 |
| 1 | 50 |
| 2 | 25 |
| 30 | 12.5 |
| 4 | 6.25 |
| 5 | 3.125 |
| 6 | 1.563 |
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