Kinetics of Drug Degradation Flashcards
What are the formulas for zero, first and second order reaction rates?
zero: v = k[A]0
first: v = k[A]1
second: v = k[A]2
What is molecurality?
the number of molecules taking part
What is the order of reaction?
number of concs that define the rate
Summarise a zero order reaction.
- rate doesnt depend on reactant conc
- conc of reactant is constant
- reservoir system eg suspension - dispersed phase can replace anything degraded as long as it is available
so rate equation is:
-dC/dt = k(C)0 which makes -dC/dt = k
integration gives C = C0 - kt
What does a line equation of a zero order graph tell you?
y = mx + c
C = -kt + C0
y intercept tells u Co
How do you find k of a zero order graph? What are the units?
-dC/dt = k
units = conc time-1
Summarise a first order reaction.
rate defined by one conc
so rate equation is:
-dC/dt = k(C)1 which makes -dC/dt = kC
integration gives C = C0.e-kt
written as lnC = lnC0 - kt
What do you do with a first order reaction to produce a straight line?
plot as natural log - lnconc
What does a line equation of a first order graph tell you?
y = mx + c
lnC = -kt + lnC0
y intercept tells u lnCo
How do you find k of a first order reaction? What are the units?
- dC/dt = kC
- dC/dtC = k
- 1/dt = k
units: t-1
What is a psuedo first order reaction?
two concs involved, but one is in excess so conc is not expected to changes, so its a first order rxn
k’
Summarise a second order reaction.
depends on two concs
-dC/dt = k(C)2
integration gives 1/C = 1/C0 + kt
How do you plot a second order reaction as a straight line?
plot 1/C as a function of time
should give a positive gradient as its 1/C
What does a line equation of a second order graph tell you?
y = mx + c
y intercept tells u 1/C0
y tells you 1/C
How do you find k of a second order reaction?
- dC/dt = kC2
- dC/dt.C2 = k
- 1/dtC = k
units: conc-1time-1
