Exercise 14 Post-Lab Quiz KEY
1.
Which of the following functional groups makes a substance more soluble in lipids?
A) sulfide
B) carboxylic acid
C) alcohol
D) NONE of them
2.
How does the polarity and water solubility of a substance affect the length of time it’s retained in the body?
A) more polar, less time
B) more polar, more time
C) more water soluble, less time
D) more water soluble, more time
E) A and C
3.
To what types of solutes is the blood-brain barrier permeable to?
A) polar
B) non-polar
C) large
D) small
E) B and D
4.
How is the distribution or partition coefficient (Kd) of a substance determined?
A) By determining the relative concentration of a solute dissolved in two immiscible solvents that have been
mixed together
B) by adding a known amount of substance to a mixture of two solvents of different polarity and determining how
much substance is left undissolved after mixing the solvents
C) by adding a known amount of the substance to two different solvents of similar polarity and determining how
much substance dissolved in each solvent
D) by reacting it with a base or acid and then performing an acid-base titration
E) NONE of them
5.
What kind of information can be obtained from the distribution coefficient (Kd) of a substance?
A) relative solubility of the substance in two solvents of different polarity
B) the relative amounts of the substance that distributes itself within the various compartments/tissues of the
human body
C) the rate at which a substance is eliminated from the human body
D) ALL of them
6.
What’s the most efficient way to perform an extraction to maximize the amount of solute extracted?
A) multiple extractions with smaller volumes
B) one single extraction with a large volume
7.
How can one determine which layer is which during an extraction?
A) finding the density of the two solvents
B) adding a small amount of one of the solvents
C) BOTH A and B
D) NONE of them
8.
A student performing a similar extraction experiment to the you performed obtained the following data:
mass of organic compound (MW = 138.12) = 0.427 g
final volume of stock solution = 250.0 mL
sample taken for extraction = 50.0 mL
volume of dichloromethane used for extraction = 25.0 mL
volume of 0.01258 M NaOH consumed in titration of aqueous phase = 12.19 mL
Based on the information given, what is the value of Kd of for this organic compound?
A) 2
B) 3
C) 6
D) 9
0.427g
grams in 50.0 mL aqueous aliquot=
× 50.0 mL = 0.0854 g
250.0 mL
g
138.12
mol
grams remaining in water = 0.01258M 12.19 mL ×
= 0.0212 g
mL
1000
L
grams in organic phase = 0.0854 g – 0.0212 g = 0.0642 g
0.0642 g
0.0642 g 50.0 mL
×
=6
Kd = 25.0 mL =
0.0212 g
25.0 mL 0.0212 g
50.0 mL
9.
What's the effect of adding more water to the sample of aqueous solution taken for extraction BEFORE the extraction?
A) less solute will migrate to the organic solvent because the higher volume of water reduces the
concentration of the aqueous layer
B) less solute will migrate to the organic solvent because the higher volume of water increases the concentration of
the aqueous layer
C) more solute will migrate to the organic solvent because the higher volume of water reduces the concentration of
the aqueous layer
D) more solute will migrate to the organic solvent because the higher volume of water increases the concentration
of the aqueous layer
E) it has no effect
10. What’s the effect of adding more water to the sample of aqueous solution taken for extraction AFTER the extraction
(before the titration)?
A) less solute will migrate to the organic solvent because the higher volume of water reduces the concentration of
the aqueous layer
B) less solute will migrate to the organic solvent because the higher volume of water increases the concentration of
the aqueous layer
C) more solute will migrate to the organic solvent because the higher volume of water reduces the concentration of
the aqueous layer
D) more solute will migrate to the organic solvent because the higher volume of water increases the concentration
of the aqueous layer
E) it has no effect
11. REFER TO THE STRUCTURES OF SERTRALINE (A) AND ATORVASTATIN (B) ON PAGE 14-10 OF YOUR
LAB MANUAL TO ANSWER THIS QUESTION. The half-life (t1/2) of a drug in the human body is the time required
for the drug's blood concentration to decrease by one half. Sertraline (Zoloft-TM) is an anti-depressant that acts as a
selective serotonin reuptake inhibitor (SSRI) in the central nervous system. Deficiency of the neurotransmitter serotonin
in the CNS is believed to be one of the causes of depression and this drug works by raising the brain levels of serotonin.
Atorvastatin (Lipitor-TM) is a lipid-lowering agent that specifically inhibits the cellular (i.e., endogenous) synthesis of
cholesterol. Examine the chemical structures of these two drugs and predict which one would have a longer half-life in
the body, given that drugs having a higher lipid solubility and molar mass typically take longer to clear.
A) sertraline  LESS POLAR (LONGER HALF-LIFE)
B) atorvastatin
12. REFER TO THE STRUCTURES OF DIAZEPAM (A) AND HYDROCHLOROTHIAZIDE (B) ON PAGE 14-10 OF
YOUR LAB MANUAL TO ANSWER THIS QUESTION. Diazepam (Valium-TM) is an agent commonly used for
treating anxiety, insomnia, and seizures. It's one of several drugs belonging to the general class called benzodiazepines,
which act in the CNS. Hydrochlorothiazide (HCTZ, Esidrex-TM) is a thiazide diuretic (i.e., "water pill" that induces
urination) that inhibits the reabsorption of sodium in the distal convoluted tubules of the kidneys and in that manner
increases the output of salt and water into the urine, thus decreasing the fluid content of the body. HCTZ is commonly
used in the treatment of edema (swelling) and hypertension (high blood pressure). Which is more likely to cross the
blood-brain barrier and why?
A) diazepam because it's less soluble in water
B) diazepam because it's more soluble in water
C) HCTZ because it's less soluble in water
D) HCTZ because it's more soluble in water
13. What physically happened to the benzoic acid when you shook a separatory funnel containing CH2Cl2 and an aqueous
solution of the acid acid?
A) it was completely transferred into the CH2Cl2
B) it became deprotonated upon reacting with the CH2Cl2
C) its concentration in the aqueous phase decreased because it migrated into the CH2Cl2
D) NONE of the above
14. What factors influence the process described in the previous question?
A) polarity
B) intermolecular forces
C) BOTH of them
D) NONE of them
15. Which of the following represents the reaction between aqueous benzoic acid (Ph–CO2H) and aqueous NaOH?
A) Ph–CO2H + NaOH → Ph–CO2– +Na + H2O
B) Ph–CO2H + H2O → Ph–CO2– + H3O+
C) Ph–CO2H + Na → Ph–CO2– + NaH