CHEM/PHYS
What expression gives the average amount of current (in amps) that flows through the agarose gel if 8.5 x 10^-4 moles of H2(g) are produced in 900 seconds (15 minutes)? (Note: F = 9.6 x 10^4 C mol^-1) A. (8.5 x 10^-4) x 2 x (9.6 x 10^4)/(9.0 x 10^2) B. (8.5 x 10^-4) x (9.6 x 10^4)/(9.0 x 10^2) C. (8.5 x 10^-4) x 4 x (9.6 x 10^4)/15 D. (8.5 x 10^-4) x 2 x (9.6 x 10^4)
A. (8.5 x 10^-4) x 2 x (9.6 x 10^4)/(9.0 x 10^2) Based on the stoichiometric coefficients of the reduction reaction, 2 moles of electrons are transferred for each mole of H2(g) that is formed.
What range corresponds to the expected chemical shifts of the adamantane protons in the 1H NMR spectrum of Compound 4? A. 1.0-2.0 ppm B. 2.5-4.5 ppm C. 4.5-6.5 ppm D. 7.0-8.0 ppm
A. 1.0-2.0 ppm The passage and the structure of Compound 4 in Figure 1 indicate that the adamantane substituent is a hydrocarbon (made of carbon and hydrogen atoms). Aliphatic protons are surrounded by an electron cloud and shielded from B0, resulting in an upfield chemical shift typically below 2 ppm. Therefore, the signals for the protons in the adamantane substituent in Compound 4 appear between 1.0 and 2.0 ppm.
What is the IUPAC name for the following molecule, which could be used as an alternative reagent for the acylation in Step 4? A. 2,2-dimethylbutanoic anhydride B. 2-ethyl-2-methylpropanoic anhydride C. 2,2-dimethylbutanoic ether D. 2,2-dimethylbutanoic ester
A. 2,2-dimethylbutanoic anhydride
In the 1H NMR spectrum of mechlorethamine, what is the signal area ratio for proton environments found on carbons directly bonded to the nitrogen atom? A. 4 to 3 B. 8 to 3 C. 2 to 2 to 3 D. 4 to 4 to 3
A. 4 to 3 Mechlorethamine contains a tertiary nitrogen, in which two of the three alkyl groups are identical (-CH2CH2Cl) due to the plane of symmetry. Consequently, the atoms directly bonded to the nitrogen atom are in one of two chemical environments- Environment A: two CH2 groups (2 x 2 H = 4) Environment B: one CH3 group (1 x 3 H = 3) Therefore, the signal area ratio is 4 to 3
In the 1H NMR spectrum of mechlorethamine, which of the following statements most accurately describes the relationship between the chemical shift of proton environment A and proton environment B? A. Proton environment A has a higher chemical shift than proton environment B B. Proton environment B has a higher chemical shift than proton environment A C. Proton environments A and B have identical chemical shifts D. Nothing can be inferred about the relative chemical shift of proton environments A and B
A. Proton environment A has a higher chemical shift than proton environment B Since environment (B) a primary carbon is less substituted than environment A (a secondary carbon), the chemical shift of environment A is expected to be higher. In addition, the electronegative chlorine atom is closer to environment A, leading to greater inductive deshielding and a higher chemical shift for environment A. Together, these data point toward the conclusion that proton environment A has a higher chemical shift than proton environment B
Many of the bonds in vitamin K have angles of 120 degrees. Which reaction in Figure 1 results in one or more new bonds with angles of less than 120 degrees? A. Reaction 1 only B. Reaction 2 only C. Reaction 3 only D. Reactions 1 and 2 only
A. Reaction 1 only All the carbon atoms in the ring structures of vitamin K have bond angles of 120 except the carbons involved in the epoxide. Because the epoxide is formed by Reaction 1, only Reaction 1 is expected to cause bond angles to change from 120 to less than 120.
If 1.40 g sample of ammonium chloride is placed in 25.0 mL of N-methylformamide at 25 degrees Celsius, the sample will: A. fully dissolve to form an unsaturated solution, because the amount of the sample will not exceed its solubility limit B. fully dissolve to form a saturated solution, because the amount of the sample will exactly reach its solubility limit C. partially dissolve to form a saturated solution, because the amount of the sample will exceed its solubility limit. D. not dissolve at all, because the sample is completely insoluble in the solvent
A. fully dissolve to form an unsaturated solution, because the amount of the sample will not exceed its solubility limit 1.40 g NH4Cl/25.0 g x 4/4 = 5.60 g NH4Cl/100 g solvent 5.60/100 < 5.89/100
If the temperature of the concentration cell increases, the magnitude of Ksp will: A. increase B. decrease C. equal zero D. remain constant
A. increase The passage states that the dissolution of BaSO4(s) is endothermic. As such, the heat absorbed from the dissolution reaction can be written as a reactant in the chemical equation. Therefore, increasing the temperature of the concentration cell will cause Ksp to increase as the reaction shifts toward the product (ie, solubility increases)
In the 1H NMR spectrum of Compound 4, the protons bonded to the carbon atom marked with an asterisk appear as a: A. singlet B. doublet C. triplet D. quartet
A. singlet The carbon atom in Compound 4 marked by an asterisk is a -CH2 group bonded to a quarternary carbon atom and a tertiary amine. As such, the -CH2 group has no neighboring hydrogen atoms (N = 0) and N + 1 = 1. Therefore, the CH2 group is not coupled to any adjacent protons and appears as a singlet in the 1H NMR spectrum
In Reaction 1, what hybridization state changes do the methylated carbon atom in the ringed structure of vitamin K hydroquinone and the oxygen atom involved in epoxide formation undergo? A. sp2 to sp3 for the methylated carbon and sp2 to sp3 for the oxygen atom B. sp2 to sp3 for the methylated carbon and sp to sp2 for the oxygen atom C. sp2 to sp3 for the methylated carbon and sp2 to sp2 for the oxygen atom D. sp to sp2 for the methylated carbon and sp2 to sp3 for the oxygen atom
A. sp2 to sp3 for the methylated carbon and sp2 to sp3 for the oxygen atom
In cisplatin, the oxidation number of platinum is: A. 0 B. +2 C. +4 D. +6
B. +2 [Pt(NH3)2Cl2] = 0 net charge Pt + 2(-3) + 6(+1) + 2(-1) = 0 Pt - 6 + 6 - 2 = 0 Pt = +2
What is the approximate molar concentration of the saturated BaSO4(aq) solution? (Note: Use 233 g/mol for the molar mass of BaSO4 and 1.0 g/mL for the density of water.) A. 1.0 x 10^-8 M B. 1.0 x 10^-5 M C. 2.4 x 10^-3 M D. 5.6 x 10^-1 M
B. 1.0 x 10^-5 M 2.4 x 10^-4 g/100 g x 1 mol BaSO4/233 g BaSO4 x 1000 mL/1 L = 1.0 x 10^-5 M BaSO4
What is the change in blood pressure over a 10 cm long section of the aorta? (Note: Viscosity of blood is n = 2 mPa x s A. 10 Pa B. 3.2 Pa C. 1.0 Pa D. 0.8 Pa
B. 3.2 Pa delta P = 8QnL/pir^4 delta P = 8 (20)(2 mPa)(10)/(1)^4 = 3200 mPa = 3.2 Pa
Which of the following modifications to the experimental procedure to prepare the solutions will most likely increase the amount of ammonium chloride that dissolves in the amide solvents in Table 1? (Note: The dissolution of ammonium chloride is endothermic). A. Decreasing the pH of the solution B. Decreasing the pOH of the solution C. Adding a small amount of ammonium bromide salt D. Cooling the solution as the ammonium chloride is added
B. Decreasing the pOH of the solution Changing the pH or pOH of a solution can affect the solubility of compounds that have an acidic or basic ion. This occurs by disrupting the solubility equilibrium according to Le Chatelier's principle through acid-base reactions with the ion
Which extraction procedure would be most useful to isolate mechlorethamine from a mixture? A. Extract mechlorethamine into an organic layer from an acidic aqueous layer B. Extract mechlorethamine into an acidic aqueous layer from an organic layer C. Extract mechlorethamine into a basic aqueous layer from an organic layer D. Extract mechlorethamine into an organic layer from a basic aqueous layer
B. Extract mechlorethamine into an acidic aqueous layer from an organic layer Since the passage states that mechlorethamine is unstable under basic conditions, the best choice is to extract mechlorethamine into an acidic aqueous layer from an organic layer
Which of the following species are formed at the cathode? I. Fe3+ II. OH- III. Fe2+ IV. H+ A. I and II only B. II and III only C. I, II, and IV only D. II, III, and IV only
B. II and III only Water is simultaneously reduced to OH-(aq) (and H2 gas) at the C(s) surface. Therefore, both Fe2+ and OH- are formed at the C(s) cathode
Which layer in the B&D and GC methods in Figure 2 is expected to contain sterols isolated from the Y. lipolytica extract? (Note: Assume that the majority of the alcohols are retained in the aqueous layers.) A. L1 in the B&D method and L2 in the GC method B. L2 in the B&D method and L1 in the GC method C. L1 in the GC method and L1 in the B&D method D. L2 in the GC method and L2 in the B&D method
B. L2 in the B&D method and L1 in the GC method Chloroform is denser than the aqueous layer whereas ethyl acetate is less dense than the aqueous layer. Therefore, the sterols isolated from Y. lipolytica, are found in L2 in the B&D method and L1 in the GC method
What type of chemical transformation is taking place in Step 2? A. Hydrolysis B. Lactonization C. Reduction D. Lactamization
B. Lactonization A lactonization is a condensation reaction between an alcohol and a carboxylic acid that forms a cyclic ester (lactone)
Which of the following will occur if a corrective lens is unable to form a clear image of a nearby subject? A. The focal length will shift away from the eye's lens B. The focal length will shift closer to the eye's lens C. Spherical aberration will increase D. Optical power will decrease
B. The focal length will shift closer to the eye's lens Hyperopia describes the refractive error that results in an individual being unable to see nearby objects. Hyperopia is caused by the optical power of the eye being insufficient relative to the length of the eye; the condition is corrected by placing a converging lens in front of the eye
How will the rate of DNA migration through the gel be affected if the gel is run with deionized water rather than LiC2H3O2(aq)? A. The rate of migration will remain the same B. The rate of migration will decrease to zero C. The rate of migration will increase D. The rate of migration is unrelated to the electrolyte solution used
B. The rate of migration will decrease to zero Molecular liquids such as deionized H2O(l) are nonelectrolytes because they do not dissociate into ions and do not convey electrons through the gel. Therefore, replacing LiC2H3O2(aq) with deionized H2O(l) would prevent current flow, and the rate of DNA migration through the gel would be zero (ie, no movement through the gel).
Which chemical species acts as the reducing agent in the net reaction for the mechanism in Figure 1? A. cis-[Pt(NH3)2Cl4] B. Thioglycolate C. Chlorothioglycolic acid D. Cisplatin
B. Thioglycolate
If Compound 1 is a substituted derivative of acetophenone, what is the IUPAC name of acetophenone? A. Methyl phenyl ketone B. 1-Benzylethanone C. 1-Phenylethanone D. 1-Phenylmethanone
C. 1-Phenylethanone *For acetophenone, the parent chain contains two carbon atoms and is called ethanone.
How many grams of lithium acetate were mixed in 500 mL of water to prepare the 5.0 x 10^-3 M lithium acetate solution? (Note: The molar mass of lithium acetate is 66 g/mol. A. 3.8 x 10^-5 g B. 2.5 x 10^-3 g C. 1.6 x 10^-1 g D. 1.6 x 10^2 g
C. 1.6 x 10^-1 g 0.500 L x 5.0 x 10^-3/1 = 2.5 x 10^-3 mol 2.5 x 10^-3 mol x 66 g/mol = 0.16 g
If Reaction 1 represents the most common process while obtaining a mass spectrum of mechlorethamine, which product mass-to-charge ratio (m/z) peak will have the highest abundance in the compound's mass spectrum? A. 49 B. 51 C. 106 D. 108
C. 106 Since a mass spectrum only detects charged particles (cations), only m/z 106 and m/z 108 will be detected. Of these, the m/z 106 peak will be the most abundant given the 75% natural abundance of the smaller 35Cl isotope
Which of the following aqueous solutions can be added to the reaction to separate the amide and carboxylic acid products through extraction (Note: R1 and R2 = long hydrocarbon chains) A. 5% NaCl B. 5% CH3CO2H C. 5% NaHCO3 D. 5% CH3OH
C. 5% NaHCO3 To separate the products of the reaction, extraction with a weak base such as 5% NaHCO3 will deprotonate the carboxylic acid. The resulting carboxylate anion will enter the polar aqueous layer, and the amide will remain in the organic layer.
What is the solubility of NH4Cl in N-methylacetamide expressed as grams NH4Cl per 100 grams of solvent? (Note: The molar mass of NH4Cl is 53.5 g/mol A. 0.050 g/100 g solvent B. 0.094 g/100 g solvent C. 5.0 g/100 g solvent D. 5.9 g/100 g solvent
C. 5.0 g/100 g solvent 0.90 mol NH4Cl x 53.5 NH4Cl solute = 48.2 g NH4Cl solute 0.0482 g x 1/0.96 g = 0.050 g NH4Cl solute/1 g 0.050 g NH4Cl x 100/100 = 5.0 g NH4Cl/100 g
Based on Table 1, which of the following statements does NOT correctly describe a conclusion that can be made about the melting point of prepared chalcone derivatives? A. Halogenated products have a lower melting point than ether-containing products B. Compounds with hydrogen bond donors do not have the highest melting points C. An increase in alkyl groups increases the melting point of the product D. Nothing can be inferred about the relationship of electron-withdrawing groups on the melting point
C. An increase in alkyl groups increases the melting point of the product
In Scheme 1, what is the role of the potassium hydroxide? A. Basic catalyst for a condensation reaction only B. Basic catalyst for an elimination reaction only C. Basic catalyst for both a condensation and an elimination reaction D. Acidic catalyst for a condensation reaction only
C. Basic catalyst for both a condensation and an elimination reaction
When the power source is connected to the platinum electrodes, which of the following statements are true? I. DNA migrates toward the anode II. pH increases locally at the cathode III. Acetate ions move toward the cathode IV. O2(g) evolves at the anode A. I and II only B. II and III only C. I, II, and IV only D. II, III, and IV only
C. I, II, and IV only
Compared to the solubility of the ammonium chloride in pure formamide, what effect would dissolving KCl into the formamide have on the solubility of ammonium chloride in the solvent? A. The solubility of the ammonium chloride would increase B. The solubility of the ammonium chloride would be unchanged C. The solubility of the ammonium chloride would decrease D. The effect of the added KCl salt cannot be determined without more information.
C. The solubility of the ammonium chloride would decrease Adding KCl to the formamide would produce a common-ion effect in which the added Cl- ions would shift the NH4Cl equilibrium to the left and lower the amount of NH4Cl that would dissolve (ie, the solubility of the NH4Cl would decrease).
Suppose the HPLC experiment used to generate Figure 3 is repeated, but the sample is contaminated. If the results include a new peak with a retention time of 23.421 minutes, the contaminant most likely: A. has a lower affinity for the stationary phase than vitamin K quinone B. has a lower affinity for the stationary phase than vitamin K 2,3-epoxide C. has a lower affinity for the mobile phase than vitamin K 2,3-epoxide D. has a lower affinity for the mobile phase than vitamin K hydroquinone
C. has a lower affinity for the mobile phase than vitamin K 2,3-epoxide The new peak has a longer retention time than vitamin K 2,3-epoxide, indicating that the contaminant has a lower affinity for the mobile phase (and a higher affinity for the stationary phase) than vitamin K 2,3-epoxide has
The electrolysis of water is a: A. spontaneous process with delta G > 0 and E cell < 0 B. spontaneous process with delta G < 0 and E cell > 0 C. nonspontaneous process with delta G > 0 and E cell < 0 D. nonspontaneous process with delta G < 0 and E cell > 0
C. nonspontaneous process with delta G > 0 and E cell < 0
In Experiment 1, which aqueous solutions could be included in the extraction protocol to cause phosphatidylethanolamine, then 2,6-dimethoxyphenol to sequentially enter the aqueous layer? A. 0.05 M NaOH(aq), then 0.01 M H2SO4(aq) B. 0.01 M NaHCO3(aq), then 0.05 M HCl C. 0.01 M H2CO3(aq), then 0.05 M NaHCO3(aq) D. 0.05 M H2SO4(aq), then 0.01 M NaOH(aq)
D. 0.05 M H2SO4(aq), then 0.01 M NaOH(aq) Phosphatidylethanolamine contains an amine group that can be protonated to form a water-soluble ammonium salt; therefore, a strong acid such as H2SO4 should be first used to protonate the amino group. In contrast, 2,6-dimethoxyphenol has a weakly acidic phenol group (pKa = 10) that must be deprotonated to form an ionic salt. Only strong bases such as NaOH can deprotonate phenols
If the solubility of ammonium chloride dissolved in N,N-dimethylformamide is expressed in parts per million (ppm), what is the numerical value? A. 0.0017 B. 0.17 C. 1.7 D. 1,700
D. 1,700 0.17/100 x 10^6 = 0.0017 x 10^6 = 1,700
Based on the NMR resuults described in the passage, what effect does the addition of calcium ions have on the protons that corresponded to the 1 ppm peak A. Calcium ions cause additional splitting of the 1 ppm peak B. Calcium ions reduce the splitting of the 1 ppm peak C. Calcium ions result in shielding of the protons that corresponded to the 1 ppm peak D. Calcium ions result in deshielding of the protons that corresponded to the 1 ppm peak
D. Calcium ions result in deshielding of the protons that corresponded to the 1 ppm peak The reduction of this peak and the appearance of a downfield peak upon addition of calcium ions suggest that calcium ions cause deshielding of the corresponding protons
Based on Figure 2, which amino acid residue in FIX most likely undergoes carboxylation during Reaction 1? A. Aspartate B. Asparagine C. Glutamine D. Glutamate
D. Glutamate Glutamate is a negatively charged, polar amino acid with a three-carbon side chain containing a carboxylic acid
The addition of which solution(s) to the half-cell containing the saturated BaSO4(aq) solution will result in a decrease in BaSO4(s) solubility? I. Ba(NO3)2 II. K2SO4(aq) III. BaCl2(aq) IV. NaCl(aq) A. IV only B. I and IV only C. III and IV only D. I, II, and III only
D. I, II, and III only
Which of the following stretching vibrations is expected to occur at the highest wavenumber in the infrared spectrum of mechlorethamine? A. The N-C stretch B. The C-C stretch C. The C-Cl stretch D. The C-H stretch
D. The C-H stretch The highest wavenumber stretching vibration occurs for the bond with the lightest combined mass of atoms. Of the given choices, C-H is the only bond between a heavy atom and a light atom. Therefore, the C-H stretching absorption will have the highest wavenumber.
Which of the following statements best explains why IR spectroscopy could be used to conform the structure of Compound 2? A. Different types of bonds absorb IR radiation at different frequencies, causing electronic excitations that distinguish the different functional groups in the compound. B. Different types of bonds absorb IR radiation at different frequencies, causing molecular fragmentation patterns that identify the different functional groups in the compound. C. The absorption of IR radiation by molecules causes molecular rotations at different frequencies, allowing for functional group identification D. The absorption of IR radiation by molecules causes intramolecular stretching and bending vibrations of different bond types at different frequencies, allowing for functional group identification.
D. The absorption of IR radiation by molecules causes intramolecular stretching and bending vibrations of different bond types at different frequencies, allowing for functional group identification.
The transformation taking place in Step 3 is necessary to: A. deprotect the alcohol and ensure the stereoselectivity of the Step 4 acylation. B. protect the alcohol and ensure the stereoselectivity of the Step 4 acylation C. deprotect the alcohol and ensure the regioselectivity of the Step 4 acylation. D. protect the alcohol and ensure the regioselectivity of the Step 4 acylation
D. protect the alcohol and ensure the regioselectivity of the Step 4 acylation
In the schematic diagram shown in Figure 1, electrons flow toward: A. the barium sulfate half-cell because [Ba2+ cathode] < [Ba2+ anode] B. the barium nitrate half-cell because [Ba2+ cathode] < [Ba2+ anode] C. the barium sulfate half-cell, because [Ba2+ cathode] > [Ba2+ anode] D. the barium nitrate half-cell, because [Ba2+ cathode] > [Ba2+ anode]
D. the barium nitrate half-cell, because [Ba2+ cathode] > [Ba2+ anode] According to the passage, the cathodic half-cell is filled with barium nitrate whereas the anodic half-cell has only two drops of barium nitrate. Therefore, the molar cell concentration [Ba2+] is greater in the cathodic half-cell than in the anodic half-cell. As a result, the barium anode will undergo oxidation to increase [Ba2+].
Myopia (nearsightedness)
Describes a visual condition in which the eye forms an image of distant objects at a focal point in front of the retina. Correcting myopia shifts the image away from the lens
Based on the solubility data in Table 1, what is the solubility product constant Ksp for ammonium chloride in N,N-dimethylformamide? A. 9.0 x 10^-4 B. 3.0 x 10^-2 C. 6.0 x 10^-2 D. 1.2 x 10^0
Ksp = [NH4+] [Cl-] = (0.03) (0.03) = (3 x 10^-2) (3 x 10^-2) = 9 x 10^-4
Spherical aberration
Refers to the optical deficiencies of lenses with perfectly spherical surfaces. The surfaces of the cornea or lens are not perfectly spherical, so no spherical aberration occurs
In the oxidation of vitamin K hydroquinone to vitamin K 2,3-epoxide, hydroxyl groups are converted to carbonyls. Compared to the carbon-oxygen bonds of the hydroxyl groups, the carbonyl carbon-oxygen bonds are characterized by: A. decreased overall bond length B. longer total bond length C. side-to-side overlap of p orbitals D. increased bond rotation
The pi bond is made from side-to-side overlap of p orbitals and is found in the carbonyl but not the hydroxyl group
Assume that the aorta is a straight, uniform pipe closed at one end. Which expression gives the fundamental resonant frequency (in Hz) for this pipe? (Note: Assume the speed of sound in air v = 360 m/s) A. (1 x 360)/(4 x 30) B. (1 x 360)/ (2 x 30) C. (1 x 360)/(4 x 0.3) D. (1 x 360)/(2 x 0.3)
wavelength n = 4 L/n f1 = v/4L f1 = (1 x 360)/(4 x 0.3)