AAMC MCAT test 9 a

If the reaction tube described in the passage is 2 cm in diameter and an initial helium–metal mixture displays ideal gas behavior, which of the following expressions gives the number of

9R SOLUTIONS FROM AAMC

Physical Sciences

1 1 A solution contains 0.1 M Mg2+(aq), 0.1 M Ca2+(aq), and 0.1 M Sr2+(aq) All three ions can be precipitated if which two reagents are added to the solution?A

) Reagents 1 and 2

B

) Reagents 1 and 3

Mg2+ can be precipitated from a solution of Reagent 1 only Ca2+ can be

precipitated from a solution of reagents 3 or 4, and Sr2+ can be precipitated from a solution of reagents 2, 3, or 4 All three ions can be precipitated from a solution containing Reagent 1 and reagents 3 or 4 The ions will precipitate from a solution containing reagents 1 and 3 Thus, B is the best answer

CaCO3 Thus, D is the best answer

Solution

Guess

3 The students added Reagent 2 to a test tube containing 0.1 M Ca2+(aq) and 0.1 M Sr2+(aq) Which of the following procedures will best enable the students to recover a fairly pure sample of SrSO4(s) from this mixture?

Guess

5 A solution contains either Ca2+(aq) or Sr2+(aq) Which of the following

actions will best enable the students to identify the ion in the solution?

A

) Performing a flame test

As time increases, charging must increase as well Further, the charging of a

capacitor is an exponentially decreasing process that must reach a constant value after a long time The graph in B most clearly shows this behavior Thus, B is the best answer

) remain the same

Electrical force depends on the particle’s charge and the strength of the electric field experienced by the particle, not on the particle’s speed Thus, B is the best answer.C

) increase by a factor of 2

D

) Increasing the area of the capacitor plates

Capacitance C depends on geometric factors only, and in the case of parallel plates,

C is proportional to the plate area and inversely proportional to the separation distance of the plates Thus, D is the best answer

Solution

Guess

9 A charged particle with a mass of m and a charge of q is injected midway between the plates of a capacitor that has a uniform electric field of E What is the acceleration of this particle due to the electric field?

) It accelerates toward the positive plate.

Opposites attract, so the negatively charged particle will move toward the positive plate Because there is a constant force qE on the particle, it will accelerate toward the positive plate Thus, C is the best answer

The –OH group in ETOH gives ETOH the capability of donating hydrogen bonds to water MTBE is incapable of donating hydrogen bonds to water Thus, C is the best answer.

The six hydrogen atoms in CH3OCH3 on the left side of the equation must be

balanced by giving H2O on the right side of the equation a coefficient of 3 The two

carbon atoms in CH3OCH3 on the left side of the equation must be balanced by giving CO2 on the right side of the equation a coefficient of 2 Now, the seven oxygen atoms on the right side of the equation must be balanced by giving O2 on the left side of the equation a coefficient of 3 Thus, D is the best answer.

properties of MTBE Thus, C is the best answer

18 If one mole of each additive shown in Table 1 undergoes complete

combustion, which compound requires the least amount of oxygen?

A

B

The compound with the lowest carbon-to-oxygen ratio will require the least amount

of oxygen for combustion ETOH has only two carbon atoms and one oxygen atom Thus, B is the best answer

A

) harmonic frequencies of a pipe are independent of its diameter

The passage gives the relationship between frequency and pipe geometry and shows

it being dependent on length only This makes A correct and B incorrect C is

eliminated because the velocity is explicitly given as a function of gas density D is incorrect because gas density falls with height Thus, A is the best answer

Only C is given as a possibility in the passage, namely, the quantization of the

resonant frequencies This is in fact the basis for the analogy to the pipe Thus, C is the best answer

) stellar atmospheres are open to space, so that pressure and

temperature are independent of volume

This item is fairly subtle in that only D is correct based on the passage The gas is in

an excited state but not completely ionized, making A incorrect B is entirely

incorrect, and C is true only for the gas velocity, not for the pressure wave velocity Thus, D is the best answer

Solution

Guess

22 The surface temperature of one of the observed stars is 6000 K The fraction

of its surface hydrogen atoms having electrons in energy level 2 then increases by how much for each 1 K temperature rise?

A

) (6001/5999)6 1.002, so 2 parts in 1000

B

) (6001/6000)6 1.001, so 1 part in 1000

The passage states that the population increases with T6 For an initial surface

temperature of 6000 K, an increase in 1 K must result in a population increase that is the ratio of the new temperature to the old temperature raised to the 6th powerThus, B is the best answer

) Hydrogen bonds form between H2O molecules

H2O is capable of forming intermolecular hydrogen bonds, but H2S, H2Se, and H2Te are not Thus, A is the best answer

25 If the second floor and the top floor of a building are separated by a distance

of 100 m, what is the approximate difference between the air pressures of the two levels? (Note: Air density = 1.2 kg/m3 and gravitational acceleration = 10 m/s2 Neglect the compressibility of air.)

(density) • g • (change in height)

or (1.2)(10)(100) = 1200 N/m2 Thus, D is the best answer

) It is chemically inert and has no effect on the rate

Helium is chemically inert and does not affect the metal–hydrocarbon reactions Thus, A is the best answer

Guess

28 If the reaction tube described in the passage is 2 cm in diameter and an initial helium–metal mixture displays ideal gas behavior, which of the following expressions gives the number of moles of He in the tube at 1.1 torr and 298 K? (Note: R = 0.082 L atm K–1 mol–1.)

P = 0.98 × 1.1 torr × 1 atm/760 torr

V = volume of the tube = π × (1 cm)2 × 73 cm × 1 L/1000 cm3

T = 298 K

Thus, D is the best answer

Solution

Guess

29 What does a nonlinear plot of ln [M] versus t indicate about the concentration

of the hydrocarbon (HC) and the reaction mechanism?

30 According to Table 2 and information in the passage, the reactivity of

platinum (5d96s1) relative to gold (5d106s1) is attributable to the metal–HC

interaction, which involves:

table Thus, C is the best answer.

To form the hybrid orbitals, the valence s and d orbitals must have similar energies

Ta reacts slowly, suggesting that the difference in its valence s and d orbitals’

energies is too great The valence s orbital will be lower in energy Thus, B is the best answer

33 Which of the following expressions gives the percent mass of hafnium (Hf) in

an initial mixture of He–Hf at 0.5 torr?

At 0.5 torr, the mole fraction of He is 0.93 and the mole fraction of Hf is 0.07

% mass Hf = [mass Hf/(mass Hf + mass He)] × 100%

Substitute the following:

mass Hf = 0.07 mol Hf × 178.5 g/mol Hf

mass He = 0.93 mol He × 4.0 g/mol He

Thus, C is the best answer

) constant and zero

In Experiment 1, the tire and axle are expected to remain at rest until the rope’s pull exceeds the maximum static friction force between the tire and the road; then the rope’s pull will decrease to a value equal to the kinetic friction force between the tire and the road The data in Table 1 shows an increasing force during the first 5 s, so for the time interval 0–4 s, the rope’s pull must be balanced by static friction, leaving the tire and axle at rest Thus, D is the best answer

) is equal to the magnitude of work required to stop the tire.

The work–energy theorem states that the change in the kinetic energy of a system is equal to the work done on the system The work done on the system is that needed

to stop the tire, and the change in the kinetic energy is equal to the initial kinetic energy (because the final kinetic energy is zero) Thus, B is the best answer

40 Which of the following mixtures, with each component present at a

concentration of 0.1 M, has a pH closest to 7?

) HClO(aq) and NaClO(aq)

When the acid and conjugate base concentrations are equal, the pH of a buffer equals the pKa of the acid The pKa’s of the acids can be estimated on the basis of the Ka values in Table 1 The pKa of HClO is closest to 7 Thus, A is the best answer

A

) A slight (<0.1 pH unit) increase

The pH will increase because a strong base is added The increase will be small because the base is being added to a buffer solution Thus, A is the best answer.

) NO2– is hydrolyzed with the formation of OH –(aq) ions

The NO2- reacts with water, forming OH- ions Thus, A is the best answer

A and B are ruled out because they are inverses of each other and depend only on L,

g, and H C is ruled out because wave velocity is a property of the water only D is logical because the pressure drop at one end of the lake will cause a change in the water’s equilibrium level there, and this change is directly related to a seiche’s amplitude Thus, D is the best answer

Solution

Guess

45 The principal restoring force responsible for maintaining the sloshing

oscillations in a body of “dry water” for which surface tension is very small is the:A

A

) 50π s

B

) 200π s

The period of oscillation T is

Thus, B is the best answer

C

) 300π s

D

fundamental vibration), v will be

Thus, D is the best answer

Solution

Guess

48 It was argued in the passage that certain simplifying assumptions led to the equation for frequency, which gives frequencies no more than 10% different from the observed seiche frequencies This equation would prove to be greatly in error,

) liquid that is very viscous

The passage explicitly states that the frequency equation given in the passage is only good if the viscosity is ignored, which cannot be done in C The conditions in the other options will not affect the validity of the approximation Thus, C is the best answer

D

) liquid with zero surface tension

Guess

49 Assume that a pan of “dry water” is momentarily disturbed Which of the following concepts best explains why the resulting sloshing oscillations persist for a fairly long time?

A

) Energy conservation

Although some friction (energy loss) will take place, energy will be very nearly

conserved over each oscillation period As a result, the amplitude of the seiches will decay very slowly as mechanical energy is turned into heat The other options do not pertain to the sloshing oscillations Thus, A is the best answer

eliminated Thus, B is the best answer

51 In which of the following does sound travel most rapidly?

) Equal work in both actions

The work done is mgΔh, and because none of these values changes in magnitude when the mass goes up or down, these actions involve the same amount of work Thus, C is the best answer

According to the table, the oxidation of Na has a potential of +2.71 V and the

reduction of Cl2 has a potential of +1.36 V The standard emf for the galvanic cell is therefore +2.71 V + 1.36 V = +4.07 V Thus, C is the best answer

) The ultraviolet radiation is absorbed by molecules that then fluoresce

at yet shorter wavelengths

D

) The ultraviolet radiation is absorbed by molecules that then fluoresce

at yet longer wavelengths

D is physically possible (although fluorescence does not limit the light to being blue), and so it could explain the bluish color of EQLs C cannot occur (energy is not

conserved), and options A (sodium emits yellow, not blue) and B (shorter

wavelengths, not longer, are more affected) are not reasonable Thus, D is the best answer

) the process occurs too rapidly for heat loss to be appreciable

Rapid processes are adiabatic, leaving little time for heat to be lost B and C do not make physical sense D may be true but is not relevant to the question Thus, A is the best answer

B

) the heat is carried on the advancing wavefront.

This requires straightforward knowledge of the visible spectrum The visible spectrum ranges from 400 to 700 nm, and light with wavelengths above ~620 nm is red This means that a wavelength of 6.56 x 10-7 m (656 nm) is in the red part of the

spectrum Thus, D is the best answer

octahedral geometry Thus, A is the best answer.

Equation 4 shows that 4 mol Al is produced from 2 mol Al2O3

100,000 g Al × (1 mol Al/27 g Al) × (2 mol Al2O3/4 mol Al) × (102 g/mol Al2O3) = 188.9 kg Al2O3

Thus, B is the best answer

) At the cathode in both cells

Reduction of the Al3+ to form Al(s) occurs at the cathode both in a galvanic and in an electrolytic cell Thus, B is the best answer

In Equation 2, 2 mol Al(OH)3 is produced from 1 mol CO2 It follows that 3 mol

Al(OH)3 is produced from 1.5 mol CO2 At 1 atm and 0ºC, the volume of 1.5 mol CO2

is (22.4 L / 1 mol) × 1.5 mol = 33.6 L Thus, D is the best answer

Solution

Guess

67 Changing which of the following will change the focal length of the convex mirror in Figure 2?

A

) Index of refraction of the mirror

B

) Radius of curvature of the mirror

The focal length of the mirror depends only on the radius of the curvature Because there is no refraction, the index of refraction is irrelevant and the properties of Lens B will not affect the focal length of the mirror Thus, B is the best answer

68 As the light passes from the air into the glass, it makes an angle qa in air and

an angle ql in the lens material, relative to the normal at the surface What equation relates the angles ql and qa?

The converging lens in Figure 1 is removed and the diverging lens is placed in

position B, as shown in the figure below Which of the following best describes the light rays from the diverging lens in this configuration?

A

) Converging rays

) some of the light passes through the mirror, and, by energy

conservation, potential energy is produced

C

) some of the light is absorbed by the mirror, and, by energy

conservation, thermal energy is produced

In general some of the light energy will be absorbed by the mirror, causing some heating to take place (although the amount will be small for a high-quality optical mirror) Thus, C is the best answer

B

) is absorbed and re-emitted by the nucleus of the material in the optically dense medium

) 1:2

B

) 1:3

The magnitude of the electric field E of a point charge is given by

If q is tripled, E also will be tripled Thus, B is the best answer

A (2 N) does not fall between these values Thus, A is the best answer.

75 A student plans to add HCl to a solution containing Pb(NO3)2(aq) To

determine how much Pb2+ will precipitate from solution when the HCl is added, the student needs to know which of the following?

To determine how much Pb2+ will precipitate, the student must know the solubility

of PbCl2, which is related to the solubility product constant Ksp of PbCl2 Thus, C is the best answer

Guess

77 When an element undergoes β decay, a nuclear neutron is converted to a nuclear proton as the nucleus emits an electron What happens to the atomic number and atomic mass of an element that undergoes β decay?

A

) The atomic number increases, but the atomic mass stays

approximately the same

An electron has a negative charge and very little mass compared to the charge and mass of nucleons If an electron is emitted by a nucleus to balance the charge, the nucleus must gain one positive charge (a proton); thus, the atomic number (number

of protons in nucleus) increases by one However, the atomic mass is nearly

unchanged because an electron has only 0.05% of a proton’s mass Thus, A is the best answer

) The atomic number decreases, but the atomic mass stays

approximately the same

78 The passage discussion of male and female experience assumes that:B

) there is a degree of similarity between female and male experience.The following statement emphasizes that there is a degree of similarity between male and female experience, even in the face of differences: “That such experiences [male and female] differ, there can be no disagreement; but that such experiences overlap, there should also be no disagreement”

79

) portray women struggling to achieve identity in a patriarchy

The main theme of the passage is the struggle of women for identity in a patriarchy:

“There is by now a sizable body of fiction that focuses on female experiences or conditions, in which women must find their way personally, professionally, socially, in what is basically a patriarchy This term we may define as any society in which men control authority and determine the roles women should or should not play” This theme is augmented by the passage discussion of how Bertha in Jane Eyre represents

“the characteristic victim of a male-dominated society” It is further augmented by the passage author’s reference to Virginia Woolfe’s discussion of how certain of the older generic and stylistic forms of writing are unsuited to women and how the novel was new enough to be amenable to women’s use

Solution

Guess

81 The author suggests that Bertha’s imprisonment in the upper reaches of Thornfield:

1 could have been explored equally well by male or female novelists

2 provided Jean Rhys with an archetypal symbol of the plight of women

3 functioned for Charlotte Brontë primarily as a plot device

D

) II and III only

The passage author comments that, according to Rhys’s view, “Bertha’s plight is more archetypically female than Jane’s, by far, because Jane is moving in a fairy tale

of sorts in which elements yield to her, whereas Bertha has moved in the real world

of power” Bertha also functions as a plot device and “is presented as the element that must be eliminated in order for Rochester and Jane to complete their destiny together” The passage author goes on to suggest that this was determined by the genre: “Because Charlotte Bronte was writing a romance, Bertha could become expendable”

82 According to the passage, Virginia Woolf believed the novel was more suitable

to women writers than was the epic or the poetic play because the:

) novel was a more recent and thus more flexible genre

The passage author refers to Virginia Woolfe’s discussion in A Room of One’s Own of the suitability for women of certain sentences written by men along with older

literary forms such as the epic and poetic play The author quotes Virginia Woolfe as follows: “[A]ll the older forms of literature were hardened and set by the time she became a writer The novel alone was young enough to be soft in her hands”

83 In order for the process described in paragraph 3 to occur, the

temperature of ice crystals in a cloud must be higher than that of:

D

) the supercooled droplets

The author notes that ice crystals evaporate the supercooled droplet; therefore, it logically follows that the ice crystals would need to be warmer for this process to occur

84 According to the passage, a cloud is formed when:

C

) humidity turns a large number of dust particles into water droplets.High relative humidity is a key factor in cloud formation: “When the relative humidity is high, water vapor condenses on many particles and begins to form droplets An actual cloud materializes when humidity reaches a certain critical value which turns most of the dust particles into water droplets”

85 On the sole basis of the passage, one could conclude that it might be

possible to reduce the rainfall in a region by:

B

) decreasing the number of particles in the air

The amount of water condensing on dust particles in the air and forming clouds accounts for rain, according to the passage: “An actual cloud materializes when humidity reaches a certain critical value which turns most of the dust particles into water droplets Under the right conditions, the cloud droplets combine rapidly into raindrops .” Another theory is that large dust nuclei sweep up the smaller ones and grow into the size of a raindrop: “A cloud will produce rain, according to this theory, when it contains sufficient moisture and a suitable number of giant nuclei” According to both theories, it logically follows that a decreased number of particles in the air would decrease the chances for rain

86 The passage assertion that salt is largely responsible for rainfall from warm clouds is based on evidence that:

1 salt particles are spread throughout the atmosphere

2 the amount of salt in rainfall is related to the amount of salt carried inland from the sea

3 the number of drops per unit volume in rain over the sea is similar to that of salt particles in ocean air

D

) I, II, and III

The passage indicates that all three of these conditions exist: salt particles are spread throughout the atmosphere; “there is a statistical evidence of a

relationship between the amount of salt carried inland from the sea and the amount of salt in our rainfall”; and a finding indicates that “the number of drops per unit volume in rain over the sea is about the same as the number of salt particles in the ocean air”.

86 Which of the following statements most strongly challenges the author’s

assertions about the way raindrops are formed in clouds at subfreezing temperatures?

88 Assume that a particular inland region in a warm climate receives a great deal

of rain Given the information in the passage, which of the following proposed

explanations of this phenomenon is the LEAST plausible?

A

) There is very little wind over the region

According to the passage, salt particles act as nuclei that are instrumental in the formation of raindrops and precipitation Wind is indicated in the passage as being instrumental in carrying salt particles over land Therefore, a lack of wind over the region makes it far less likely that the rain-producing salt particles would be carried inland

Solution

Guess

89 The passage suggests that the example of an eighteenth-century

American businessperson who succeeded in a competitive market but did NOT fit comfortably into a self-governing society would best support the view of:

B

) de Tocqueville

In commenting about how Crèvecoeur failed to see “that a purely economic person would be as unsuited to a self-governing society as would the rank-bound subject of traditional regimes”, the author suggests that de Tocqueville “gave a much more adequate view” The author later specifies how de Tocqueville viewed the purely economic man by commenting that de Tocqueville “appreciated the commercial and entrepreneurial spirit [in the U.S.] but saw it as having

ambiguous and problematic implications for the future of American freedom”

90 According to the passage, de Tocqueville thought that the key to

America’s success as a republic was its:

D

) citizens’ moral and intellectual dispositions

The author points out that de Tocqueville believed that mores (moeurs), the “habits

of the heart,” shaped the mental habits and the moral and intellectual disposition that contributed the most to the American character

91 The passage suggests that de Tocqueville’s analysis of America might have been more accurate than Crèvecoeur’s because de Tocqueville possessed:

B

) a belief in republican principles

De Tocqueville’s belief in republican principles is underscored by the author’s

discussion of how mores, more than even laws or physical circumstances,

contributed to maintaining the American democratic republic The author further maintains that this is a fuller, more “adequate view” than Crèvecoeur’s: “[De

Tocqueville] added to Crèvecoeur’s earlier sketch a more penetrating and complex understanding of the new society, informed by republican convictions and a deep sensitivity to the place of religion in human life”

91 According to passage information, which of the following factors would be

the best example of the “mores” of which de Tocqueville speaks in

1 the economic development of Americans

2 the French Revolution and its aftermath

3 conditions in English mill towns

C

) II and III only

In discussing de Tocqueville’s views, the author is explicit on this point: “For de Tocqueville, the optimism of the Enlightenment had been tempered by the

experience of the French Revolution and its aftermath, and the prophecies of the early political economists were finding an alarmingly negative fulfillment in the industrial infernos of English mill towns”

94 On the basis of the passage, a comparison of Crèvecoeur’s and de

Tocqueville’s views of America might reasonably lead to the conclusion that:

self-emancipated, enlightened individual confidently directing energies toward the

environment, both natural and social, aiming to wring from it a comfortable

happiness” However, the author points out that Crèvecoeur could not see what many Americans of his time saw, namely, “that a purely economic person would be unsuited to a self-governing society .” De Tocqueville found reason for pessimism where Crèvecoeur found reason for optimism: “[De Tocqueville] appreciated the commercial and entrepreneurial spirit that Crèvecoeur had emphasized but saw it as having ambiguous and problematic implications for the future of American freedom”.

95 Which of the following conclusions can justifiably be drawn from the passage?

1 Crèvecoeur believed that economic advancement was linked to individual interest

2 De Tocqueville believed that undermining American mores would threaten the country’s free institutions

3 Crèvecoeur and de Tocqueville both predicted a swift demise for the American experiment

C

) I and II only

The author comments that Crèvecoeur saw economic well-being as timed to the rational, self-interested individual The author quotes Crèvecoeur as follows: “ ‘Here the rewards of [the American’s] industry follow with equal steps the progress of his labour; his labour is founded on the basis of nature, self-interest; can it want a

stronger allurement’”? The author states that de Tocqueville stressed how American mores “had been the key to the Americans’ success and that undermining

American mores was the most certain road to undermining the free institutions of the United States”

96 According to the passage, the reason the La Mojarra writing system is thought

to have been more phonetic than the Mayan system is that:

A

) fewer glyphs were used in the La Mojarra writing system

The author points out: “The La Mojarra (Olmec) language may have fewer signs than Maya and may thus represent an even more phonetic, less logographic system”

97 Is Schele’s interpretation of Mayan concerns directly supported by

evidence presented in the passage?

D

) No; it is not explicitly supported by passage information

The author indicates that monument carving ceased before these concerns arose, thus leaving behind no revealing record Therefore, Schele’s reasons remain

speculative

98 According to passage information, which of the following factors

distinguishes the Maya from the Aztecs?

B

) The Maya probably created their own writing system

Passage information makes no indication that the Aztecs developed their own writing system whereas the author indicates that inscriptions on monuments provided evidence for the similarities between Mayan and Aztec civilizations as bloody and warlike societies In this sense, the passage makes a distinction