Chapter 12 Multiple Choice Questions

. A drug suspension decomposes by zero-order kinetics with a rate constant of 2 mg mL^-1 month^-1. If the initial concentration is 100 mg mL^-1, what is the shelf life (t_10%)?

2 months

3 months

4 months

5 months

. Which one of the following strategies would not normally be expected to reduce the rate of oxidation of an API?

Replacing the air in the package with nitrogen

Addition of a heavy metal to the formulation

Reducing the temperature of the formulation

Protecting the formulation from light

. Which one of the following is not a characteristic of a zero-order drug decomposition reaction?

The rate of reaction is constant

The rate of reaction is independent of the concentration of any of the reactants

The half-life of the drug decomposition is directly proportional to the initial concentration of API.

The units of the rate constant (k) are time^-1

. When the results of a drug degradation study are plotted on a graph, a plot of the logarithm of the amount of API remaining against time gives a straight line. Which one of the following is true?

The units of the rate constant (k) are concentration^-1 time^-1

The reaction is zero-order

The half-life may be represented by t_0.5 = 0.693/k

The half-life is directly related to the initial concentration of the reactant

. Which one of the following represents the relationship between rate constant, k, and absolute temperature, T, as predicted by the Arrhenius equation?

A plot of log k against 1/T will be linear

A plot of log k against T will be linear

A plot of k against T is linear with a negative slope

A plot of k against T is linear with a positive slope

. Regarding zero-order reactions, which one of the following is true?

The half-life may be represented by the expression t_0.5 = 0.693/k

The rate of degradation is independent of the concentration of the reactant(s)

A plot of the concentration remaining against time is a straight line with a gradient of 1/k

The units of the rate constant (k) are time^-1

. A drug solution decomposes via first-order kinetics with a rate constant, k, of 0.0077 days^-1. What is the half-life of the drug in solution?

0.033 day

33 days

70 days

90 days

. This question concerns a tablet that has remained in storage for 2 years since manufacture. From the drug monograph the decomposition rate constant (k) was found to be 6 x 10^-2 year^-1. The degradation reaction is known to proceed via first-order kinetics. Which one of the following is the remaining percentage of the original drug concentration?

94

89

83

78

. Regarding second-order kinetic processes, which of the following is true?

The units of the rate constant (k) are conc^-1

The half-life may be represented by the expression t_0.5 = [A]₀/2k

The half-life does not depend on the initial concentration of the reactants.

The rate law is of the general form v = k[A]² or v = k[A][B].

. A drug has the initial concentration of 5.0 x 10^-3g cm^-3 in aqueous solution. After 24 months, the concentration drops to 3.48 x 10^-3 g cm^-3. This degradation process is known to follow first-order kinetics. Which one of the following is the rate constant for this reaction:

-1.5 x 10^-2 month^-1

1.5 x 10^-2 month^-1

3.2 x 10^-2 month^-1

3.0 x 10^-2 month^-1

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