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What is chemical kinetics?
The study of reaction rates and the factors affecting them
What does the reaction rate measure?
The change in concentration of a reactant or product over time, typically in mol L−1s−1.
How is the initial rate of reaction determined?
From the slope of the concentration vs. time graph at t = 0
What is the rate law of a reaction?
An equation expressing the reaction rate as a function of reactant concentrations: Rate=k[A]m[B]n.
What is the rate constant (k)?
A proportionality constant dependent on temperature but independent of reactant concentrations
What determines the units of k?
The reaction order; for a first-order reaction, kk has units of s−1; for second-order, mol−1Ls−1.
What is a zero-order reaction?
A reaction where the rate is independent of reactant concentration: Rate=k.
Define a first-order reaction.
A reaction where the rate is directly proportional to the reactant concentration: Rate=k[A].
What is a second-order reaction?
A reaction where the rate depends on the square of one reactant or the product of two reactant concentrations: Rate = k[A]^2 or k[A][B].
Write the integrated rate law for a zero-order reaction.
[A]=[A]0−kt
What is the integrated rate law for a first-order reaction?
ln[A]=ln[A]0−kt or [A]=[A]0e−kt
Provide the integrated rate law for a second-order reaction.
1[A]=1[A]0+kt.
Define the half-life (t1/2).
The time it takes for the concentration of a reactant to decrease to half its initial value
What is the formula for the half-life of a first-order reaction?
:t1/2=0.693kt, independent of initial concentration
How does the half-life of a second-order reaction depend on initial concentration?
t1/2=1k[A]0, inversely proportional to initial concentration
What is the Arrhenius equation?
k=Ae−EaRT, where Ea is the activation energy, R is the gas constant, and T is temperature in Kelvin
How is the activation energy calculated graphically?
From the slope of a plot of lnk vs. 1/T: slope=−EaR.
What is an elementary reaction?
A single-step reaction that describes a specific molecular event
What determines the rate law for an elementary reaction?
The molecularity, or the number of molecules colliding in the reaction step
What is the rate-determining step?
The slowest step in a reaction mechanism, which limits the overall reaction rate
Name the types of complex reactions.
Reversible, consecutive, and parallel reactions
How do consecutive reactions proceed?
One product of the first reaction serves as the reactant for the next reaction
What is a parallel reaction?
A reaction where one reactant forms multiple products through different pathways
What is the role of a catalyst in a reaction?
To increase the reaction rate by lowering the activation energy without being consumed
What is heterogeneous catalysis?
Catalysis where the catalyst and reactants are in different phases
Provide an example of homogeneous catalysis.
Acid-catalyzed ester hydrolysis, where both catalyst and reactants are in the same phase
How is kinetics applied in pharmacokinetics?
To study the absorption, distribution, metabolism, and elimination of drugs
Why is kinetics important in drug stability studies?
To predict shelf life and determine proper storage conditions
What is the significance of accelerated stability testing?
It uses elevated temperatures to predict drug degradation rates
How is the Arrhenius equation used in pharmacy?
To estimate the shelf life of drug products by analyzing temperature-dependent reaction rates
