AAMC 1 - Chem/Phys Flashcards
How does the concentration of solute affect the migration rate in paper chromatography?
Migration rate is not affected by concentration.
The solute concentration will affect the size of spots on a paper chromatogram, not the average migration rate.
How can one increase the size of spots that appear in paper chromatography or TLC?
They can increase the concentration of solute
The solute concentration will affect the size of spots on a paper chromatogram, but not the average migration rate.
Is it possible to adjust the concentration of the stationary phase in a chromatography set-up?
No.
The stationary phase does not have a concentration as it is an immobilized surface, not a solution.
What does the thickness of filter paper affect in a paper-chromatography setup?
The thickness of the paper will affect the amount of each component that can be fully separated, but not the relative migration rates of the components.
True or False:
Tertiary alcohols readily dehydrate
True.
If a reaction leads to a mixture of cis- and trans-alkenes, is the reaction stereospecific?
No, this is enough evidence to conclude that the reaction is NOT stereospecific.
The functional group that represents a peptide bond is called an _______ group.
The functional group that represents a peptide bond is called an amide group.
In gas-liquid chromatography, what are the properties of the compound that makes the first peak observed in the GC trace?
In gas-liquid chromatography, the first peak to emerge will be from the least polar, most volatile compound.
Least polar, lowest boiling point
Which compound is stronger, an alkyl halide or an alkene?
Alkyl halide is stronger.
Alkyl halides are polar, so they can interact with themselves through dipole-dipole forces as well as london dispersion forces.
Alkenes are non-polar, therefore they can only interact with themselves through london dispersion forces.
For this reason, alkenes will have a lower boiling point.
What is deuterium, and where would it fall when ranking priority to assign absolute configuration?
Deuterium is an isotope of Hydrogen that contains one proton as well as a neutron. Standard H does not contain a neutron. When assigning priority, we can not use atomic number as they are identical, so the tie is broken my atomic mass. Deuterium has atomic mass of 2, so it is higher priority than Hydrogen but lower than everything else.
What kind of substitution reaction results in an inversion of stereochemistry 100% of the time?
SN2 reactions invert stereochemistry 100% of the time.
What kind of substitution reaction creates a racemic mixture of products, and why?
SN1 reactions produce racemic mixtures of products. This is because a leaving group will leave first, creating a carbocation. At this point, the substituting molecule can attack the carbocation from either side, creating a racemic mixture.
What is the stereochemistry of this molecule?
R
O is the highest priority, followed by the carbon chain, followed by Deuterium (Hydrogen + neutron), and lastly H
What would be the stereochemistry of this molecule after an SN2 reaction?
Before the reaction, the molecule is R. Oxygen is the highest priority, followed by the carbon chain, followed by Deuterium (Hydrogen + neutron), and lastly H.
SN2 reactions result in the inversion of stereochemistry 100% of the time. Therefore this would be an S absolute configuration.
Which reactions between the carboxylic acid or the primary alcohol loses the -OH group in an esterification?
The -OH from the carboxylic acid will be lost, while the O from the alcohol will be the oxygen in the ester linkage.
A person, whose eye has a lens-to-retina distance of 2.0 cm, can only clearly see objects that are closer than 1.0 m away. What is the strength S of the person’s eye lens? (Note: Use the thin lens formula .)
A. –50 D
B. –10 D
C. 51 D
D. 55 D
Solution: The correct answer is C.
- The negative sign of the lens strength is indicative of a diverging lens, whereas the eye lens is a converging lens.
- The negative sign of the lens strength is indicative of a diverging lens, whereas the eye lens is a converging lens.
- According to the thin lens formula, the strength of the eye lens is equal to the inverse of the focal length of the eye lens. Its numerical value is given by (1 m)−1 + (0.02 m)−1 = 1 D + 50 D = 51
- This answer implies the person can only clearly see objects that are closer than 20 cm away.
What does a enzyme stabilize in order to affect reactions?
An enzyme stabilizes the transition state, thus lowering the activation energy of a reaction.
An enzyme stabilizes the _________, thus lowering the activation energy of a reaction.
An enzyme stabilizes the transition state, thus lowering the activation energy of a reaction.
Which of the following will decrease the percentage ionization of 1.0 M acetic acid, CH3CO2H(aq)?
A. Chlorinating the CH3 group
B. Diluting the solution
C. Adding concentrated HCl(aq)
D. Adding a drop of basic indicator
C. Adding concentrated HCl(aq)
- Replacing H with Cl will stabilize the formation of negative charge on the nearby carboxylic acid group. This is because chlorine is an electronegative atom. This change will therefore increase the percentage ionization of the acid.
- Diluting the solution will increase the percentage ionization by Le Châtelier’s Principle.
- HCl is a strong acid that will increase the amount of H+ in solution and thus decrease the percentage of CH3CO2H that ionizes.
- Adding a drop of basic indicator will slightly increase the amount of dissociated (ionized) acid due to the acid−base reaction that occurs between the two.
Knowing that the speed of light in the vitreous humor is 2.1 × 108 m/s, what is the index of refraction of the vitreous humor? (Note: The speed of light in a vacuum is 3.0 × 108 m/s.)
A. 0.7
B. 1.4
C. 2.1
D. 3.0
The correct answer is B
- This option implies light travels faster through the vitreous humor than through vacuum, which is a scientific impossibility.
- The index of refraction of a medium is equal to the ratio of the speed of light in vacuum to the speed of light in the medium, thus in this case is equal to (3.0 × 108 m/s)/(2.1 × 108 m/s) = 1.4.
- This is 50% larger than the index of refraction of the vitreous humor, which is equal to (3.0 × 108 m/s)/(2.1 × 108 m/s) = 1.4.
- The index of refraction of the vitreous humor is equal to (3.0 × 108 m/s)/(2.1 × 108 m/s) = 1.4; however, this (3.0) number is 114% larger.
What is the energy of the photons emitted by the LED at a frequency of 610 THz? (Note: h = 6.6 × 10–34 J·s)
A. 9.2 × 10–12 J
B. 1.6 × 10–16 J
C. 1.1 × 10–18 J
D. 4.0 × 10–19 J
D. 4.0 × 10–19 J
The energy of a photon of frequency 610 THz is equal to 6.6 × 10−34 J•s × 610 x 1012 Hz = 4 × 10−19 J.
note: Tera = x 1012
What is the work generated by a healthy adult who circulates 9 L of blood through the brachial artery in 10 min? (at 900 ml/min there is 200 W of work done)
We’re given blood in liters in our question stem, so we can use dimensional analysis to convert to mL. 1000 mL in 1 L tells us the adult circulates 9000 mL of blood / 10 minutes. Simplifying here gives us 900 mL/min.
We are told at 900 ml/min there are 200 W of work done.
Work is power x time, so we can multiply the power generated (200 W) by time (600s) to get 120,000 J or 120 kJ.
Why is the velocity of blood flow slower in capillaries than in arteries?
A. Capillary walls are more elastic than arterial walls.
B. Capillaries have less resistance to blood flow than arteries.
C. The total cross-sectional area of capillaries exceeds that of arteries.
D. Blood pressure is higher in the capillaries than in arteries.
C. The total cross-sectional area of capillaries exceeds that of arteries.
The high number of capillaries in the body means that the total cross-sectional area of these vessels is larger than any other vessel type in the circulatory system. This causes the velocity of the blood to decrease.
Which of the following types of orbitals of the central atom are involved in bonding in octahedral compounds?
A. sp
B. sp3
C. p
D. d2 sp3
D. d2sp3
Octahedral compounds have six σ bonds and no stereochemically active lone pairs. According to valence bond theory, the central atom requires the hybridization of six atomic orbitals, d2sp3.