Physics section test (1)

In each experiment, evolved gases were collected in the following apparatus: a rubber tube was connected at one end to a reaction vessel; the free end of the tube was inserted into colle

MCAT Section Tests

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Physical Sciences

Test 1

Time: 40 Minutes

Number of Questions: 31

PHYSICAL SCIENCES

DIRECTIONS: Most of the questions in the following Physical Sciences test are organized into groups, with a descriptive passage preceding each group of questions Study the passage, then select the single best answer to each question in the group Some of the questions are not based on a descriptive passage; you must also select the best answer to these questions If you are unsure of the best answer, eliminate the choices that you know are incorrect, then select an answer from the choices that remain Indicate your selection by blackening the corresponding circle on your answer sheet A periodic table is provided below for your use with the questions

PERIODIC TABLE OF THE ELEMENTS

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Physical Sciences 1

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Passage I (Questions 1–8)

Malachite is a green semiprecious stone with the

molecular formula CuCO3 • Cu(OH)2 Malachite is

widespread in nature, occurring near copper deposits,

and can also be synthesized in the laboratory

Three experiments were carried out to investigate

some of the chemical properties of malachite In each

experiment, evolved gases were collected in the

following apparatus: a rubber tube was connected at one

end to a reaction vessel; the free end of the tube was

inserted into collection bottles inverted in a tub of

water, allowing gas to displace the water in the bottle

The bottles were corked and set aside for later analysis

The following experiments were performed:

Experiment 1

A 22 g sample of malachite was placed in the

reaction vessel and the bottom of the vessel was heated

rapidly After a short time, a black solid appeared in the

bottom of the reaction vessel, condensation appeared on

the flask, and gas bubbled through the free end of the

tube into the collecting bottles The black solid was

identified as copper (II) oxide

Experiment 2

A 44 g sample of malachite was placed in the

reaction vessel, and an aqueous sulfuric acid solution

was added to the vessel Shortly, gas evolved from the

free end of the tube When the reaction was complete, a

strip of pH paper inserted into the aqueous solution in

the reaction vessel showed it to be neutral

Experiment 3

Three gas-filled collection bottles were taken from

each of the above experiments A burning splint was

inserted into the mouth of one bottle from each

experiment; in each case, the flame was extinguished

immediately Water, 25 mL, was then added to the

second bottle from each experiment, and the bottle was

corked and shaken Strips of pH paper dipped in the

water turned pink in both cases Finally, 50 mL of

calcium hydroxide solution were added to the third

bottle from each experiment, and the bottles were

shaken A milky white solution was observed in each

1 The gas collected in Experiments 1 and 2 was most

likely:

A oxygen

B water vapor

C carbon dioxide

D hydrogen

2 What is the percent composition of oxygen in

malachite?

A 29%

B 36%

C 50%

D 67%

3 The reaction that occurred in Experiment 1 can be

classified as a(n):

A acid-base reaction

B double displacement reaction

C redox reaction

D decomposition reaction

4 Assume the gas collected in Experiment 1 is pure If

the volume of each collection bottle is 100 mL, how many bottles will be needed to collect all the gas produced? (The conditions are STP.)

A 2 vessels

B 3 vessels

C 22 vessels

D 23 vessels

5 Which of the following statements is true of

Experiment 2?

A An excess of sulfuric acid was added to the

reaction vessel

B An aqueous copper sulfate solution was

formed

C An aqueous copper hydroxide solution was

formed

D The pH paper turned blue upon contact with the

reaction solution

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6 If stoichiometric amounts of calcium hydroxide

solution were used in Experiment 3, the final

solution would be:

A neutral

B acidic

C basic

D Cannot be determined

7 If Experiment 2 were performed with aqueous

hydrochloric acid rather than sulfuric acid, you

would expect the products to be:

A Cu(s), Cl2(g), CO2(g), H2O

B CuCl2(aq), H2O, CO2(g)

C HCl(aq), H2CO3(aq), H2O

D CuCl2(aq), Cu(s), H2CO3(aq)

8 When the copper oxide produced in Experiment 1

was weighed, it was found that 4 g had been

produced What was the percent yield of copper

oxide from this experiment?

A 18%

B 25%

C 50%

D 100%

Passage II (Questions 9–13)

There are situations in which matter may be converted into energy This occurs, for example, in the formation of a nucleus, the mass of which is found to be slightly less than the sum of the masses of the individual protons and neutrons Another instance in which this occurs is in the process of nuclear fusion, which describes the reaction when two smaller nuclei are brought together under certain conditions and join together to form a larger nucleus, resulting in the release

of large amounts of energy In the sun’s core, for example, 2 hydrogen atoms combine to form one helium atom By this process the sun produces 4x 1026 J of energy every second

Energy can be released not only by fusing smaller nuclei but by splitting larger ones This process is known

as nuclear fission For example, when uranium is bombarded with neutrons, it is split into two smaller nuclei and energy is released This particular nuclear reaction also releases more neutrons, which can cause further fission reactions with other uranium nuclei and thus lead to a self-sustaining chain reaction In nuclear reactors, this process is controlled by inserting control rods, made of elements such as cadmium, that absorb some of the neutrons without undergoing a fission reaction themselves

9 A typical uranium fission reaction is shown below

92

235

U + 0 1

n → 139 54

Xe+ Y + 3 0 1 n What is the product Y formed by this reaction?

A 36 94

Kr

B 9238Sr

C 38 94

Sr

D 54

139

Xe

Physical Sciences 1

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10 The total energy that it takes to separate a nucleus

into its individual protons and neutrons is called the

binding energy This energy:

A. is sufficient to sustain a chain reaction

B is equal to the total mass of the nucleus times

the speed of light squared

C is equal to the mass defect of the nucleus times

the speed of light squared

D is equal tothe kinetic energy of a β – particle

ejected during beta decay

11 The neutrons that are released during a fission

reaction are first passed through a magnetic field,

and then through an electric field They are:

A deflected by the magnetic field only

B deflected by the electric field only

C deflected by both the magnetic field and the

electric field

D not deflected at all

12 9038Srdecays by emitting an alpha particle to form a

stable isotope of krypton, 3686Kr If after 19 hours

75% of the sample has decayed, what is the half life

of the reaction?

A 4.8 hours

B 9.5 hours

C 14 hours

D 29 hours

13 Fission reactions can be initiated by bombarding

nuclei with neutrons Would bombarding with protons work just as well?

A Yes, because protons and neutrons are both

present in the nucleus

B Yes, because protons and neutrons have

approximately the same mass

C No, because protons do not have as high a

binding energy as neutrons and thus not as energetic

D No, because neutrons, unlike protons, do not

experience electrostatic repulsion from the nucleus

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Passage III (Questions 14–18)

Enzymes are biological molecules that increase

chemical reaction rates An enzyme does not change the

equilibrium constant, but merely catalyzes the reaction,

reducing the energy required to bring the substrate to the

transition state

Simple enzymes have a single catalytic site, and

their rate of catalysis is directly proportional to the

amount of substrate available, up to the point where

there is so much substrate that all the catalytic sites have

been filled This pattern produces a hyperbolic plot of

reaction velocity vs substrate concentration, with Vmax

as an asymptote To simplify calculations, this

hyperbolic graph can be transformed into a straight-line

graph, using the Michaelis-Menten equation:

1/V = (K M /Vmax)(1/[S]) + 1/Vmax

Equation 1

where V is the velocity of the reaction, [S] is the

substrate concentration, and K M, called the Michaelis

constant for the reaction, is the substrate concentration

that gives a reaction rate of Vmax/2

Figure 1

The catalytic activity of an enzyme can be inhibited

in two ways In competitive inhibition, the catalytic site

is filled by a molecule other than the substrate

Competitive inhibition can be overcome by increasing

the concentration of the substrate Noncompetitive

inhibition is caused by binding to a regulatory site other

than the catalytic site This can cause a change in the

shape of the entire molecule, interfering with its

catalytic activity

Figure 2 The following table records rates of catalysis at different concentrations of substrate for a reaction carried out with and without a noncompetitive inhibitor

Table 1

inhibitor)

1.0 x 10–5 M 10 µM / min 5.0 µM / min

1.5 x 10 –5 M 12 µM / min 6.0 µM / min

3.0 x 10 –5 M 15 µM / min 7.5 µM / min

14 The presence of an enzyme alters the:

A energy level of the reactants

B energy level of the products

C energy of activation

D change in free energy of the reaction

(0, 1/V

max )

0

x = 1/[S]

y = 1/V

slope = K M /V max

Physical Sciences 1

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15 In competitive inhibition:

A K M increases

B K M decreases

C Vmax increases

D Vmax decreases

16 In the reaction illustrated in Table 1, the effect of

the inhibitor is to:

A increase K M

B decrease K M

C increase Vmax

D decrease Vmax

17 In the biochemical pathway shown below, both B

and D are found to inhibit enzyme a Increasing the

concentration of A overcomes inhibition by B but

not by D At what locations do B and D bind to a?

A  →  a B  →  b C  →  c D

A Both bind at the catalytic site

B They bind at different regulatory sites

C B binds at the catalytic site, and D at a

regulatory site

D B binds at a regulatory site, and D at the

catalytic site

18 K M for a given reaction would vary with the:

I pH

II temperature

III concentration of enzyme

IV concentration of substrate

A I and II only

B I, II, and III only

C I, II and IV only

D I, II, III, and IV

Questions 19 through 23 are NOT

based on a descriptive passage

19 An insulated cylindrical container whose volume is

2500 cm3 is filled with water at a temperature of 30°C If the water is heated by a 2000 W immersion heater, which of the following could be a graph representing the temperature of the water as a function of time for the first 100 s, assuming a constant specific heat?

20 Which of the following elements, each in their

ground state, has a partially filled d subshell?

A B

B Si

C Mg

D Cr

21 Two identical conducting spheres on insulating

supports carry charges of magnitude +Q and +2Q

respectively When they are separated by a distance

of d the electrostatic repulsive force is F The

spheres are made to touch and then restored to their

original separation d If there is no loss of charge,

what is the new force of repulsion?

A F/2

B 3F/4

C 8F/9

D 9F/8

time

A

B

C

D

0 °C

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22 Which of the following does not have an electronic

configuration of 1s2 2s2 2p6 3s2 3p6?

A Ar

B Cl–

C K+

D Ga3+

23 A source emits light of wavelength 600 nm for

0.01 µs. How many complete waves are sent out?

(Note: Speed of light = 3 x 108 m/s)

A 5.0 x 106

B 1.8 x 108

C 5.0 x 109

D 5.0 x 1019

Passage IV (Questions 24–31)

A sports car with a total mass of 1000 kg can accelerate from rest to 28 m/s in 8 seconds The coefficient of static friction µs, which is a measure of the maximum resistance between the tires and the road when there is no sliding, equals 0.6 The coefficient of kinetic friction µk,which is a measure of the resistance between the tires and the road when the tires slide (skid), equals 0.2 The optimum braking technique is to apply the maximum possible force that is consistent with the car tires not skidding

This performance car has a sophisticated anti-lock braking system, such that if the car starts to skid, the braking mechanism is overridden, and the tires are allowed to continue turning so that they can stop skidding and regain their grip on the road At this point the brakes are automatically reapplied, as long as the driver is still depressing the brake pedal This process repeats approximately twenty times a second

The braking system itself works on the principle of the hydraulic lever When the driver presses the brake pedal, a piston exerts a force on the brake fluid The pressure that results from this force is transmitted throughout the liquid and presses against the brake shoe piston This in turn presses against the brake shoe, which applies a force on the wheel and stops the car (Note: Assume that the acceleration due to gravity (g) equals 9.8 m/s2.)

24 If the car starts from rest and maintains a constant

acceleration for 8.0 s, what is the ratio of the distance traveled in the first four seconds to the distance traveled in the last four seconds?

A 1:2

B 1:3

C 1:4

D 1:1

25 The engine of the car is turbo-charged, thereby

doubling the net force on the car The time that it takes for the car to accelerate from the rest to a speed of 28 m/s will:

A be 1/4 as long

B be 1/2 as long

C remain unchanged

D be twice as long

Physical Sciences 1

26 The coefficient of static friction µs is a measure of

the car’s ability to keep from sliding sideways

during a turn on an unbanked surface The

maximum sideways force that the car can sustain

without sliding will:

A increase if the velocity of the car increases

B decrease if the velocity of the car increases

C increase if the mass of the car increases

D decrease if the mass of the car increases

27 The area of the “contact patch” (the surface of tire

in contact with the road) for each of the tires is A If

the car is stationary on a level surface, and if each

tire provides the same support, what is the pressure

being exerted on the surface? (m = mass of the car.)

A mg

A

B mg

C mg

4A

D 4mg

A

28 The car is parked on a slope that makes an angle θ

with the horizontal If the handbrake is then

released, and the car is allowed to roll down the

slope, which of the following graphs represents the

acceleration of the car versus the displacement?

29 The car is traveling at a velocity of 24 m/s along a

level road What is the shortest time it will take for the car to come to rest? (Assume that the car does not skid, and neglect air resistance.)

A 3.1 s

B 4.1 s

C 4.8 s

D 12.2 s

30 How does the surface area of the brake shoe piston

compare to the surface area of the brake pedal piston?

A The brake shoe piston is larger so the force

exerted on the wheels is greater

B The brake shoe piston is larger to increase the

coefficient of friction between the brake shoe and the wheels

C The brake pedal piston is larger to maximize

the pressure

D The brake pedal piston is larger to increase the

contact between the brake pedal and the brake shoe

31 The car is parked on a hill when the handbrake cable

snaps, causing the car to roll down the hill into a lake If the car displaces 0.5 m3 of water, what is the apparent weight of the car? (Note: The density

of water is 1000 kg/m3.)

B 4,900 N

C 9,800 N

D 29,400 N

END OF TEST