Cop 2015 Pharmaceutics Lecture 08/18/2011
(22).webp "Cop 2015 Pharmaceutics Lecture 08/18/2011 - Quiz")
Questions and Answers
- 1.
Acid strength increases as pKa increases.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false. Acid strength actually decreases as pKa increases. The pKa value is a measure of the acidity of an acid. A lower pKa value indicates a stronger acid, meaning it is more likely to donate a proton. Conversely, a higher pKa value indicates a weaker acid, meaning it is less likely to donate a proton. Therefore, as pKa increases, the acid strength decreases.Rate this question:
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- 2.
Which is the stronger basic functional group?
- A.
Imine, pKa 3-4
- B.
Aromatic amine, pKa 5-6
- C.
Guanidine, pKa 10-11
- D.
Arylamine, pKa 4-5
Correct Answer
C. Guanidine, pKa 10-11Explanation
Guanidine is the strongest basic functional group because it has the highest pKa value of 10-11. A higher pKa value indicates a stronger basicity, meaning that guanidine is more likely to accept a proton and form a positive charge. In comparison, imine and arylamine have lower pKa values of 3-4 and 4-5 respectively, indicating weaker basicity. Aromatic amine has a slightly higher pKa value of 5-6, but it is still lower than guanidine, making guanidine the strongest basic functional group among the options given.Rate this question:
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- 3.
As pKb increases, the strength of the base also increases.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because as pKb increases, the strength of the base actually decreases. pKb is the negative logarithm of the base dissociation constant, and a higher pKb value indicates a weaker base.Rate this question:
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- 4.
As pKa increases, the strength of the base also increases.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
This statement is true because pKa is a measure of the acidity of a compound. As pKa increases, it means that the compound is less acidic and more basic. Therefore, the strength of the base increases as pKa increases.Rate this question:
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- 5.
Amphiprotic molecules are:
- A.
Mostly basic
- B.
Mostly acidic
- C.
Neither basic nor acidic
- D.
Both basic and acidic
Correct Answer
D. Both basic and acidicExplanation
Amphiprotic molecules are able to donate and accept protons, which means they can behave as both acids and bases. This dual nature allows them to react with both acidic and basic substances, making them both basic and acidic. Examples of amphiprotic molecules include water (H2O) and amino acids.Rate this question:
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- 6.
When calculating the pH of an amphiprotic solution, which of these will factor into the equation? (Two correct answers)
- A.
PKa at which the amphiprotic molecule loses a proton, pKa1
- B.
PKa at which the amphiprotic molecule gains a proton, pKa2
- C.
PKw
- D.
Concentration
Correct Answer(s)
A. PKa at which the ampHiprotic molecule loses a proton, pKa1
B. PKa at which the ampHiprotic molecule gains a proton, pKa2Explanation
When calculating the pH of an amphiprotic solution, the pKa at which the amphiprotic molecule loses a proton (pKa1) and the pKa at which the amphiprotic molecule gains a proton (pKa2) will factor into the equation. The pKa values represent the acidity or basicity of the molecule and determine whether it will donate or accept a proton. These values are essential in determining the equilibrium between the acidic and basic forms of the molecule, which ultimately affects the pH of the solution. The pKw (ionic product of water) and concentration may also play a role in the equation, but they are not the specific factors mentioned in the answer.Rate this question:
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- 7.
Adding a strong acid, such as HCl, to a weakly basic drug will produce the salt form of the drug. The product is:
- A.
A weak base
- B.
A weak acid
- C.
A strong base
- D.
A strong acid
- E.
Neutral
Correct Answer
B. A weak acidExplanation
When a strong acid, like HCl, is added to a weakly basic drug, it will react with the drug and form the salt form of the drug. In this reaction, the weakly basic drug acts as an acid and donates a proton to the strong acid. As a result, the drug is converted into its salt form, which is a weak acid. Therefore, the correct answer is a weak acid.Rate this question:
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- 8.
Adding a strong base, such as NaOH, to a weakly acidic drug will produce the salt form of the drug. The product is:
- A.
A weak base
- B.
A weak acid
- C.
A strong base
- D.
A strong acid
- E.
Neutral
Correct Answer
A. A weak baseExplanation
When a strong base, such as NaOH, is added to a weakly acidic drug, it will react with the acidic drug to form the salt form of the drug. In this reaction, the weakly acidic drug will act as an acid and donate a proton to the strong base, forming a new compound that is a weak base. Therefore, the product of this reaction is a weak base.Rate this question:
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- 9.
If you were trying to calculate the pH of the reaction below, the pKa of which molecule would be used in the calculation?
- A.
Maleic acid
- B.
Chlorpheniramine
- C.
Chlorpheniramine maleate
- D.
Water
Correct Answer
A. Maleic acidExplanation
The pKa value of a molecule is used to determine its acidity or basicity. In this question, the pH of a reaction is being calculated, which suggests that the reaction involves an acid-base equilibrium. Maleic acid is a known acid and has a pKa value, which would be used in the calculation of the pH of the reaction. Chlorpheniramine and chlorpheniramine maleate are not acids, and water is a neutral molecule, so their pKa values would not be relevant in this calculation.Rate this question:
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- 10.
If you were trying to calculate the pH of the reaction below, the pKb of which molecule would be used in the calculation?
- A.
Maleic acid
- B.
Chlorpheniramine
- C.
Chlorpheniramine maleate
- D.
Water
Correct Answer
B. ChlorpHeniramineExplanation
The pKb value of Chlorpheniramine would be used in the calculation of the pH of the reaction. The pKb value represents the negative logarithm of the base dissociation constant, which indicates the strength of a base. In this case, Chlorpheniramine is the molecule that would act as a base in the reaction, and its pKb value would be used to determine the concentration of hydroxide ions in the solution, which is necessary for calculating the pH.Rate this question:
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- 11.
In the above reaction assume the base is very strong. The reaction will favor:
- A.
The charged state
- B.
The uncharged state
Correct Answer
A. The charged stateExplanation
When the base is very strong, it will readily accept a proton from the reactant, resulting in the formation of a charged species. This charged state is more stable and favored in the reaction because the strong base has a high affinity for protons. Therefore, the reaction will favor the charged state over the uncharged state.Rate this question:
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- 12.
The pKa of a weak base is 8.3. What is the pKb for this base?
- A.
5.7
- B.
8.3
- C.
-1.3
- D.
4.7
Correct Answer
A. 5.7Explanation
The pKa of a weak base is a measure of its acidity, while the pKb is a measure of its basicity. Since the pKa and pKb are related by the equation pKa + pKb = 14, we can calculate the pKb for this base by subtracting its pKa from 14. In this case, 14 - 8.3 = 5.7, so the pKb for this base is 5.7.Rate this question:
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- 13.
The pKb for a strong base is 1.6. What is the pKa for this base?
- A.
2.6
- B.
1.6
- C.
12.4
- D.
7
Correct Answer
B. 1.6Explanation
The pKb value represents the negative logarithm of the base dissociation constant (Kb) for a base. Since a strong base has a high Kb value, its pKb value will be low. The pKa value represents the negative logarithm of the acid dissociation constant (Ka) for the conjugate acid of the base. In the case of a strong base, its conjugate acid is very weak, and therefore has a very low Ka value. Consequently, the pKa value for a strong base will be the same as its pKb value, which is 1.6 in this case.Rate this question:
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- 14.
Without knowing the pKa of each molecule, which is the strongest base?
- A.
1.
- B.
2.
Correct Answer
B. 2. -
- 15.
Resonance stabilizes electron pairs and, in some molecules, such as number 1 above, resonance stabilization contributes to the molecule being a weaker base.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Resonance stabilization refers to the delocalization of electrons in a molecule, which can result in increased stability. In the case of molecule number 1, resonance stabilization contributes to it being a weaker base. This is because the delocalization of electron pairs makes it less likely for the molecule to donate a pair of electrons and accept a proton, which is characteristic of a base. Therefore, the statement that resonance stabilization contributes to the molecule being a weaker base is true.Rate this question:
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- 16.
Which is the stronger acidic functional group?
- A.
Phenol, pKa 9-11
- B.
Sulfonic acid, pKa 0-1
- C.
Sulfonimide, pKa 5-6
Correct Answer
B. Sulfonic acid, pKa 0-1Explanation
Sulfonic acid is the stronger acidic functional group compared to phenol and sulfonimide. This is because it has a lower pKa value of 0-1, indicating a higher acidity. A lower pKa value means that the acid is more likely to donate a proton, making it a stronger acid. Phenol has a pKa of 9-11, indicating a weaker acidity. Sulfonimide has a pKa of 5-6, which is higher than sulfonic acid but still lower than phenol, making it less acidic than sulfonic acid.Rate this question:
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.png "Resonance stabilizes electron pairs and, in some molecules, such as number 1 above, resonance stabilization contributes to the molecule being a weaker base.")
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