Cop 2015 Pharmaceutics Lecture 08/17/2011

Explanation
The cation K+ does not have any direct effect on the pH of a solution. The pH of a solution is determined by the concentration of hydrogen ions (H+) present in the solution. K+ does not contribute or affect the concentration of H+ ions, so it does not have any impact on the pH. Therefore, the statement is false.

Explanation
Strong bases, such as NaOH, produce weak conjugate acids. This is because strong bases completely dissociate in water, yielding hydroxide ions (OH-) which are strong bases themselves. When a strong base reacts with water, it forms a weak conjugate acid and hydroxide ions. Therefore, the statement that strong bases produce strong conjugate acids is false.

Explanation
Fe3+ would decrease the pH of a solution because it is a strong Lewis acid that can accept a pair of electrons from a water molecule, forming a hydronium ion (H3O+). The presence of more hydronium ions in a solution increases its acidity, resulting in a decrease in pH.

Explanation
In an acid/base reaction, water is not always included in the Ka and Kb expressions as either a reactant or a product. This is because water is considered to be a solvent in these reactions and does not participate as a reactant or a product. The Ka and Kb expressions only include the concentration of the acid or base species involved in the reaction, not water.

Explanation
When transition metals are added to a solution, they tend to act as Lewis acids by accepting electron pairs from water molecules. This results in the formation of hydronium ions (H3O+), leading to an increase in the concentration of H+ ions in the solution. Therefore, the pH of the solution decreases, indicating that it becomes more acidic.

Explanation
At higher temperatures, the pKa of Fentanyl decreases from 8.22 to 8.05. This means that at the higher temperature, Fentanyl will be more uncharged compared to lower temperatures. Since uncharged molecules are more lipophilic, they can easily cross cell membranes and be absorbed more easily. This increased absorption leads to Fentanyl being more active at higher temperatures during hyperthermic treatment.

Explanation
Fentanyl exists mostly in an uncharged state during hyperthermic treatment. The pKa value of Fentanyl at both 37°C and 42°C is above the physiological pH of the body, which means that the majority of the Fentanyl molecules will remain uncharged. In an uncharged state, Fentanyl can easily cross cell membranes and reach its target sites, allowing it to be more active and induce anesthesia effectively.

Explanation
Aspirin is a weak acid that ionizes in water to form its conjugate base. The pH of the ileum is alkaline, ranging from 7.0 - 8.0. In an alkaline environment, weak acids tend to remain in their non-ionized form, which is less soluble and less readily absorbed. Therefore, aspirin is less likely to be readily absorbed in the ileum.

Explanation
The duodenum is the first part of the small intestine where the majority of digestion and absorption of nutrients takes place. It has a large surface area and is lined with villi, which are finger-like projections that increase the absorption capacity. Therefore, it is logical to assume that most drugs would be absorbed in the duodenum due to its favorable conditions for absorption.

Explanation
Aniline is a weak base, and its pKa value indicates the pH at which it is half dissociated. In this case, since the pKa is 4.6, the pH of the solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log ([A-]/[HA]). In this equation, [A-] represents the concentration of the conjugate base (Aniline-) and [HA] represents the concentration of the weak base (Aniline). Since the concentration of Aniline is given as 0.03M, and the concentration of Aniline- can be assumed to be negligible, the equation simplifies to pH = pKa + log (0.03/0.03). By substituting the values, the pH is calculated to be 8.54.

Explanation
Morphine is a basic drug, meaning it has a tendency to accept protons and become positively charged in an acidic environment. Since the stomach is an acidic environment, it is likely that morphine would exist mostly charged in the stomach. Therefore, the statement "Morphine would exist mostly charged in the acidic stomach" is true.

Explanation
The cation NH4+ is the ammonium ion, which is a weak acid. When added to a solution, it can act as an acid and donate a proton, thereby decreasing the pH of the solution. Therefore, the statement that the cation NH4+ increases the pH of a solution is false.

Explanation
When an anion, such as Cl-, is the conjugate base of a strong acid, it means that it is formed when the strong acid donates a proton. Since strong acids completely dissociate in water, the resulting anion does not have any tendency to react with water and does not affect the concentration of H+ ions in the solution. Therefore, adding the anion to a solution will not change the pH of that solution, making the statement true.

Explanation
If the pKa is less than the pKb, it means that the acid dissociation constant is smaller than the base dissociation constant. This indicates that the acid is stronger than the base in the solution. In an acidic solution, the concentration of hydrogen ions (H+) is higher than the concentration of hydroxide ions (OH-). Therefore, the given statement is true.