MCAT Section Tests Dear Future Doctor, The following Section Test and explanations should be used to practice and to assess your mastery of critical thinking in each of the section areas Topics are confluent and are not necessarily in any specific order or fixed proportion This is the level of integration in your preparation that collects what you have learned in the Kaplan classroom and synthesizes your knowledge with your critical thinking Simply completing the tests is inadequate; a solid understanding of your performance through your Score Reports and the explanations is necessary to diagnose your specific weaknesses and address them before Test Day All rights are reserved pursuant to the copyright laws and the contract clause in your enrollment agreement and as printed below Misdemeanor and felony infractions can severely limit your ability to be accepted to a medical program and a conviction can result in the removal of a medical license We offer this material for your practice in your own home as a courtesy and privilege Practice today so that you can perform on test day; this material was designed to give you every advantage on the MCAT and we wish you the best of luck in your preparation Sincerely, Albert Chen Executive Director, Pre-Health Research and Development Kaplan Test Prep © 2003 Kaplan, Inc All rights reserved No part of this book may be reproduced in any form, by Photostat, microfilm, xerography or any other means, or incorporated into any information retrieval system, electronic or mechanical without the written permission of Kaplan, Inc This book may not be duplicated, distributed or resold, pursuant to the terms of your Kaplan Enrollment Agreement Physical Sciences Test Time: 38 Minutes Number of Questions: 29 MCAT 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 H 1.0 He 4.0 Li 6.9 Be 9.0 B 10.8 C 12.0 N 14.0 O 16.0 F 19.0 10 Ne 20.2 11 Na 23.0 12 Mg 24.3 13 Al 27.0 14 Si 28.1 15 P 31.0 16 S 32.1 17 Cl 35.5 18 Ar 39.9 19 K 39.1 20 Ca 40.1 21 Sc 45.0 22 Ti 47.9 23 V 50.9 24 Cr 52.0 25 Mn 54.9 26 Fe 55.8 27 Co 58.9 28 Ni 58.7 29 Cu 63.5 30 Zn 65.4 31 Ga 69.7 32 Ge 72.6 33 As 74.9 34 Se 79.0 35 Br 79.9 36 Kr 83.8 37 Rb 85.5 38 Sr 87.6 39 Y 88.9 40 Zr 91.2 41 Nb 92.9 42 Mo 95.9 43 Tc (98) 44 Ru 101.1 45 Rh 102.9 46 Pd 106.4 47 Ag 107.9 48 Cd 112.4 49 In 114.8 50 Sn 118.7 51 Sb 121.8 52 Te 127.6 53 I 126.9 54 Xe 131.3 55 Cs 132.9 56 Ba 137.3 57 La * 138.9 72 Hf 178.5 73 Ta 180.9 74 W 183.9 75 Re 186.2 76 Os 190.2 77 Ir 192.2 78 Pt 195.1 79 Au 197.0 80 Hg 200.6 81 Tl 204.4 82 Pb 207.2 83 Bi 209.0 84 Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra 226.0 89 Ac † 227.0 104 Rf (261) 105 Ha (262) 106 Unh (263) 107 Uns (262) 108 Uno (265) 109 Une (267) * 58 Ce 140.1 59 Pr 140.9 60 Nd 144.2 61 Pm (145) 62 Sm 150.4 63 Eu 152.0 64 Gd 157.3 65 Tb 158.9 66 Dy 162.5 67 Ho 164.9 68 Er 167.3 69 Tm 168.9 70 Yb 173.0 71 Lu 175.0 † 90 Th 232.0 91 Pa (231) 92 U 238.0 93 Np (237) 94 Pu (244) 95 Am (243) 96 Cm (247) 97 Bk (247) 98 Cf (251) 99 Es (252) 100 Fm (257) 101 Md (258) 102 No (259) 103 Lr (260) GO ON TO THE NEXT PAGE as developed by Physical Sciences Passage I (Questions 1–5) The Kjeldahl method for determining the percentage of nitrogen in a substance is an important tool in industrial research It is commonly used to determine the protein content of meats, grains, fertilizers, drugs, and other biological substances Because proteins from a particular source tend to contain the same percent nitrogen, the percentage of protein in the sample can be estimated quite accurately by multiplying the percentage of nitrogen by a known factor This factor is 6.25 for meats, 6.38 for dairy products, and 5.70 for cereals The sample to be analyzed is first decomposed in hot, concentrated sulfuric acid (H2SO4), which oxidizes carbon and hydrogen to CO2 and H2O respectively Amine and amide nitrogens are quantitatively converted to ammonium ion (NH4+) The hot sulfuric acid decomposition, or digestion, proceeds slowly, especially with substances that are resistant to H2SO4 (e.g., heterocyclic compounds like pyridine) Digestion times for these compounds can often be decreased by adding a neutral salt, such as potassium sulfate (K2SO4), to the digestion mixture The digest is then cooled, and made basic with 50% NaOH This process liberates ammonia: A technician is analyzing 0.1 g of beef using the Kjeldahl procedure The final titration of the borate requires 5.5 mL of 0.01 M HCl Which of the following represents the percentage of protein in the sample? 0.01× 0.0055× 14 × 100 0.1 0.01× 0.0055× × 14 × 100 B 0.1 0.01× 0.0055× 14 × 100× 6.25 C 0.1 01× 0.055× 14 × 100× 6.25 D 0.1 A According to the Brønsted-Lowry acid-base theory, which of the following pairs shows the conjugate acid of NaOH and the conjugate base H3BO3, respectively? A B C D NH4+ + OH– → NH3(g) + H2O Reaction H2O and NH3 NH3 and NH4+ H2SO4 and H2BO3– H2O and H2BO3– This gaseous ammonia is then distilled into a flask containing an excess of boric acid, which converts the ammonia back to the ion as follows: H3BO3 + NH3 ? NH4+ H2BO3– Reaction Reaction produces an acidic solution containing the borate ion The borate ion is then titrated with standardized HCl to find the percent nitrogen Which of the following acid-base indicators would be used to find the endpoint in the titration of the H2BO3– produced in Reaction with standardized HCl? A Bromocresol green (pH of transition = 3.8 to 5.4) B Cresol purple (pH of transition = 7.6 to 9.2) C Phenolphthalein (pH of transition = 8.3 to 10.0) D Phenol red (pH of transition = 6.8 to 7.4) GO ON TO THE NEXT PAGE KAPLAN MCAT Which of the following compounds is least likely to need K2SO4 added to its digestion mixture? A B C D A guanine base A cyclic alkene A furan compound A pyrrole derivative H3BO3 can be classified as: A B C D a polyprotic acid a polyprotic organic acid the conjugate base of H2BO3– a reducing agent Passage II (Questions 6–10) Food is digested by the body in a series of steps, and the body uses the energy released at each step for body functions This is the process of metabolism The overall energy released by the metabolic process equals the energy released in the equivalent combustion process Thus, by measuring the amount of energy released during combustion, we can find the energy that a particular food provides to the body A constant-volume calorimeter, shown in Figure 1, measures the energy content of a substance The bomb, which holds the sample to be measured, is a container filled with oxygen gas at a given pressure The bomb itself resides in a thermally isolated container, which holds 2000 g of water The sample is ignited electrically, and its combustion produces heat, which the water and bomb absorb The energy content of the sample can be determined by measuring the change in temperature of the water with a simple thermometer However, before the heat or energy produced by the reaction can be calculated, it is necessary to calibrate the calorimeter: that is, the heat capacity of the bomb must be determined The heat capacity of the bomb is the product of the specific heat and the mass of the bomb (Note: The specific heat of water is 4,190 J/kg • K.) Figure A heater is placed in the calorimeter to calibrate it Which of ON the following GO TO THEphysical NEXTquantities PAGE need to be determined? as developed by Physical Sciences A The change in temperature only B The change in temperature and the power of the heater C The power of the heater and the time the heater operated D The change in temperature, the power of the heater, and the total time it operated A B C D (1620 + 2) ∞ (1620 + ∞ 4190) ∞ 275 (1620 + ∞ 4190) ∞ It cannot be determined unless the mass of the calorimeter is known Why must the container be thermally isolated ? A So all the heat released by the sample will be absorbed by the water B So all the heat released by the sample will be absorbed by the bomb and the water C So that the system will always be in thermal equilibrium D So that the system will not conduct electricity increases by 2°C when the sample is ignited, what is the heat released in joules? 10 What happens to the entropy of the calorimeter system after the combustion of a sample? A B C D It increases It decreases It remains the same It increases and then decreases If the bomb is not sufficiently thermally isolated and lets heat escape, how would it affect the calculated energy content of the food being measured? A The calculated value would be less than the actual value because the enthalpy change of combustion is maximized under adiabatic conditions B The calculated value would be less than the actual value because the observed temperature change of the water would be lower C The calculated value would be higher than the actual value because the reaction would release more heat to compensate for the heat loss in accordance with le Châtelier’s principle D The calculated value would be higher than the actual value because the heat capacity of the calorimeter would decrease A sample of 2-methyl-naphthalene is submerged in a bomb with a heat capacity of 1,620 J/°C which is submerged in a calorimeter containing kg of water If the temperature of the water KAPLAN Passage III (Questions 11–16) Titration is a common procedure used in quantitative analysis Two reagents that are often used for this purpose are potassium iodide and sodium thiosulfate Iodide is used to standardize, or establish MCAT the molarity of, a thiosulfate solution First, an aqueous solution of iodine is prepared by adding an excess of potassium iodide to a known volume of an acidic solution of potassium iodate IO3– + I– + H+ ? I2 + H2O Reaction The iodine combines with excess iodide to form triiodide, by the following reaction: I2 + I– I3– Reaction Keq = 7.1 ∞ 102 calculation indicates thiosulfate solution? the molarity of the (0.01)(0.05)(3) 32 60 (0.01)(0.05)(6) B (214.0)(0.03260) (0.01)(0.05)(6) C (0.03260) (2)(0.01)(0.05)(6) D (166.0)(0.03260) A Triiodide solutions are commonly referred to as iodine solutions since this terminology adequately explains the stoichiometry of this reagent (I2 + 2e– ? 2I–) The iodine solution resulting from Reaction is titrated with the thiosulfate solution that is to be standardized The two half-reactions that occur are: E°(V) S2O3 ? S4O6 + Reaction 2– 2– e– –0.09 I2+ e– ? I– Reaction 12 In the reaction between iodine and thiosulfate, which species are reducing agents? A B C D I2 and S4O62– S4O62– and S2O32– S2O32– and I2 S2O32– only 0.54 The endpoint of this titration is determined by adding starch, a common iodine indicator, and watching for disappearance of the deep blue starch/iodine complex The molarity of thiosulfate is then determined from the amount of iodate consumed in Reaction An application of this technique is the use of a standardized thiosulfate solution, together with potassium iodide, to determine the percentage of copper in brass A weighed sample of brass is dissolved in nitric acid, and an excess of KI is added to the acidified solution This produces the following reaction: 13 What is the standard potential for the redox reaction between thiosulfate and molecular iodine? A –0.63 V B –0.45 V C 0.45 V D 0.63 V Cu 2+ + I– ? CuI(s) + I2 Reaction The liberated iodine is then titrated with thiosulfate to the endpoint 11 g of KI (MW 166.0) are added to 50 mL of a 0.010 M KIO3 solution This solution is titrated with 32.60 mL of an unstandardized sodium thiosulfate solution (MW 158.10) Which 14 The reduction of copper (II) to copper (I) has a standard half-cell potential of only 0.15 V Considering this fact, how is it possible for copper to be reduced by iodide? GO ON TO THE NEXT PAGE as developed by Physical Sciences I The reaction is thermodynamically favored, and therefore is spontaneous II The reaction is forced to completion by an excess of iodide and by the formation of copper (I) iodide III The oxidation of iodide is favored under acidic conditions, as shown in Equation A B C D I only II only I and II only II and III only 15 The titration described in the passage determined that there were 0.01 moles of copper in 1.90 g of brass What is the percentage of copper in this brass sample? A 1% B 3% C 33% D 66% 16 If sodium hydroxide were added to Reaction 1, how would the equilibrium constant of Reaction change? A It would increase because iodide would be removed from the solution as NaI salt B It would increase because the excess water produced would lower the concentrations of iodine and iodide C It would remain the same because Reaction and Reaction are unrelated D It would remain the same because the equilibrium constant for a reaction is the same for all concentrations of reactants and products at the same temperate Questions 17 through 21 are NOT based on a descriptive passage 17 A thin converging lens of focal length 100 mm is used as a magnifying glass If the object viewed is 80 mm from the lens, how far from the lens will the image be? KAPLAN A 40 mm B 44 mm C 400 mm D At infinity 18 Which factors would you need to determine the density of oxygen in a vessel containing a mixture of gases, using the formula PV = nRT? A The partial pressure of oxygen and the number of moles of oxygen in the container B The partial pressure of oxygen and the total number of moles of gas in the container C The total pressure of gas in the container and the number of moles of oxygen in the container D The total pressure of gas in the container and the total number of moles of gas in the container 19 A train is moving at 30 m/s The conductor sounds the horn which has a frequency of 100 Hz What is the frequency that a passenger on the train hears? A 85 Hz B 100 Hz C 110 Hz D Cannot be determined 20 If 230 g of ethanol (C2H5OH) are added to 180 g of water, by how much does the vapor pressure of the water change? A B C D It decreases by 33% It decreases by 50% It decreases by 56% It decreases by 67% 21 The pressure in a non-compressible liquid: A B C D increases with depth decreases with depth depends upon the shape of the container depends upon the total volume of the fluid Passage IV (Questions 22–29) Circular particle accelerators, such as the cyclotron, have been used for over 50 years to gain a better understanding of the nature of elementary particles The cyclotron is depicted in a top view in Figure and in a side view in Figure This accelerator is composed of two hollow, metal, D- MCAT shaped containers, called dees They are connected to an alternating voltage supply Above and below the dees are electromagnets that create a uniform magnetic field Initially, charged particles are at the center of the cyclotron accelerator, which is point S in Figure Originally, one of the dees is at a positive potential, and the other is at a negative potential In the case of a positively charged particle, the particle will be accelerated towards the dee with a negative potential and will enter it Inside the dee, the electric field is zero, due to the shielding of the dee However, a magnetic force is present, which causes the particle to execute uniform circular motion By the time the particle comes to the edge of the dee, the alternating voltage has changed so that the particle now faces the negative dee, and is again accelerated by the potential difference The frequency of the particle’s circular motion can be related to the magnetic field by the equation: Figure 22 Which of the following diagrams correctly depicts the directions of the acceleration and velocity vectors of a charged particle traveling in a cyclotron dee? qB = 2? mv where q is the charge, B is the magnetic field strength, m is the mass of the charge and v is the frequency of the circular motion Note that the frequency of the particle does not depend on its speed; faster particles will travel in larger circles The frequency of the voltage supply is therefore set equal to the frequency of the particles, and both quantities remain constant A particular cyclotron is used to accelerate protons It has a radius of 0.5 m, an oscillator frequency of 10 MHz and a maximum voltage of 100 kV (Note: eV = 1.6 ∞ 10–l9 J Also, the fundamental unit of charge, e, equals 1.6 ∞ 10–l9 C and the mass of a proton is 1.6 ∞ 10–27 kg.) Figure GO ON TO THE NEXT PAGE as developed by Physical Sciences 23 If a proton travels in a clockwise direction in the cyclotron, as shown in Figure 1, what is the direction of the magnetic field created by the electromagnets? A B C D Out of the page Into the page Towards the top of the page Towards the bottom of the page 24 Which of the following correctly gives the value of the energy of a proton inside the dee in terms of the mass, m, the charge, q, the magnetic field strength, B, and the radius of the dee, r? qBr m2 q2 B2 r B 2m qBr C 2m q2 B2 r D m2 A 27 What is the ratio of the period of a proton 0.5 m from the source to one 0.25 m from the source? A B C D 1:1 1:2 2:1 4:1 28 A proton in a cyclotron moving with an energy of 10 MeV and speed of 4.4 ∞ 107 m/s strikes a stationary hydrogen ion target After the collision the target moves with a speed of 3.5 ∞ 107 m/s (6.4 MeV) and the proton moves with an energy of 0.42 MeV Which of the following statements about this collision is true? (Assume that the particles move along the same path after the collision.) A The collision is completely inelastic B The collision is completely elastic C The final speed of the incident proton is 0.9 ∞ 107 m/s D Momentum is not conserved 25 Which of the following adequately describes when the particles are accelerating? A Only inside the dees because only there does the particles’ speed changes B Only between the dees because only there does the particles’ speed changes C Throughout the entire cyclotron because the particles are changing speed between the dees and changing direction within the dees D Throughout the entire cyclotron because the particles are changing direction between the dees and changing speed within the dees 26 Which of the following equations correctly describes the voltage at a given time, t, for the cyclotron? (Note: Use units of volts and seconds.) A B C D 29 If the magnetic field in the accelerator increases, what factor must be changed to keep the final velocity of the protons constant? A B C D The oscillator frequency must be decreased The radius of the dees must be decreased The voltage must be decreased The radius of the dees must be increased END OF TEST (7 ∞ 104) sin ((2? ∞ 107)t) (105) sin (10–7 t) (105) sin (107 t) (105) sin ((2? ∞ 107)t) KAPLAN MCAT ANSWER KEY: C 11 D 12 A 13 B 14 A 15 10 10 D B B C A 16 17 18 19 20 C D C B C 21 22 23 24 25 A A A B C D C A B A 26 27 28 29 D A C B ...Physical Sciences Test Time: 38 Minutes Number of Questions: 29 MCAT PHYSICAL SCIENCES DIRECTIONS: Most of the questions in the following Physical Sciences test are organized into groups,... must be decreased The voltage must be decreased The radius of the dees must be increased END OF TEST (7 ∞ 104) sin ((2? ∞ 107)t) (105) sin (10–7 t) (105) sin (107 t) (105) sin ((2? ∞ 107)t) KAPLAN