Chemical kinetics lecture Flashcards
What are rate of reactions?
How to measure rates
What is rate laws?
How to calculate amount left or time to reach a given amount
What is stability and half life?
How long it takes to react 50% of reactants
What is arrhenius equation?
How rate constant changes with T
What is acid and base catalysis?
Mechanism of catalysis
How does kinetics play into pharmaceutical systems?
Rate of drug degradation needs to be known
Understanding stability characteristics to handle and store products
Effects of temperature, light, and catalysts on the stability of drug formulation
Possible breakdowns
More stable drug preparations
Knowledge of deterioration at various hydrogen ion concentrations allows what?
One to choose a vehicle that will retard or prevent degradation
What is thermodynamics?
Does a reaction take place?
What is kinetics?
How fast does a reaction proceed?
Define reaction rate
Change in the concentration of a reactant or a product with time (dc/dt)
dc = increase or decrease of concentration over an infinitesimal time interval, dt
The rate of a chemical reaction is proportional to the product of the ??
molar concentration of the reactants each raised to a power usually equal to the number of molecules, a and b, of the substances A and B undergoing reaciton
Define rate law
Relationship of the rate of a reaction to the rate constant and the concentration of the reactants raised to some power
What is the specific rate constant for a reaction?
The constant k appearing in the rate law associated with a single-step reaction
Define pseudo-order
One of the reactants is present in such a great excess that its concentration may be considered constant or nearly so
- Depends on only the first power
What is a zero-order reaction?
The decomposition proceeds at a constant rate and is independent of the concentration of any of the reactants
Define half-life
Time required for one half of the material to disappear; it is the time at which A has decreased to 1/2A
Zero- reaction graph ?
Linear equation plotted with [A] on the y axis and t on the x and the slope is equivalent to k
First-order reaction graph?
y axis = lnA
Second-order reaction graph?
y axis = 1/[A]
Define second-order
When A and B are present in the same concentration, the integrated form of the second order reaction
Define the substitution method
Data accumulated in a kinetic study may be substituted in the integrated form of the equations that describe the various orders
The equation is found in which the calculated k values remain constant within the limits of experimental variation, the reaction is considered to be of that order
What factors affecting reaction rate?
Concentration of reactants: Increase so does the likelihood that reactant molecules will collide
Temp: higher, more kinetic energy, move faster, and collide more
Catalysts: speed reaction by changing mechanism
Solvent
Light
What is Arrhenius equation?
k= Ae-(Ea/RT)
lnk= lnA- (Ea/R*1/T)
1/T against log k
Define activation energy
Energy barrier (hump) that must be overcome for a chemical reaction to proceed
Define shelf-life
Length of storage time before the preparation becomes unfit for use with regard to strength, through either chemical decomposition or physical deterioration
- No more than 10%l provided the decomposition product are not more toxic or harmful than the original
Define catalyst
A substance that influences the speed of a reaction without itself being altered chemically
