gen chem self assessment

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Physical Sciences

Self-Assessment:

General Chemistry Test

MCAT® is a program of the Association of American Medical Colleges

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Commitment Self-Assessment

How committed are you to completing this test and using the results to prepare for the MCAT?

1=Not committed , 2=Somewhat committed, 3=Committed

If answer is 1, --- Completing the test requires a commitment of time and energy. If you do not feel you can

commit the time to complete it, you may be better off waiting to take the test until you can commit the time. The

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unknown can be daunting. However, it is important that you feel motivated to complete the test since you need

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Pre-test Confidence Self-Assessment

One of the factors that can influence both your preparation and performance on the actual MCAT exam is your

confidence. This questionnaire will help you assess your confidence on the topics in this section of the exam so

that you can use the information to decide where you should focus your study time. You will be asked to rate

your confidence again after completing the test to help you gauge how your experience with actual MCAT

questions influences your perception of your ability in these content areas so that you can decide if you were

overconfident, under confident or on target and why this may be.

Confidence: Using the 5-point scale below in the table, how confident are you are in your ability to perform

well on this section of the MCAT exam as well as for each content category?

MCAT®

is a program of the Association of American Medical Colleges

Test/Content Categories

A=1-Not

Confident

at all

B=2-

Somewhat

Confident

C=3-

Moderately

Confident

D=4-Very

Confident

E=5-

Extremely

Confident

1. General Chemistry

Overall

2. Acids and Bases

3. Bonding

4. Electrochemistry

5. Electronic Structure

and Periodic Table

6. Kinetics and

Equilibrium

7. Phases and Phase

Equilibria

8. Solution Chemistry

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9. Stoichiometry

10. Thermodynamics and

Thermochemistry

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1 H 1.0

Periodic Table of the Elements

2

He 4.0

3 Li 6.9

4 Be 9.0

5 B

10.8

6 C

12.0

7 N

14.0

8 O

16.0

9 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)

89 Ac† (227)

104 Rf

(261)

105 Db (262)

106 Sg

(266)

107 Bh

(264)

108 Hs

(277)

109 Mt (268)

110 Ds

(281)

111 Uuu (272)

112 Uub (285)

114

Uuq (289)

116

Uuh (289)

* 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)

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Physical Sciences Self-Assessment: General Chemistry Test

Number of Questions: 104

Approximate Time to Complete: 2-3 hours

Welcome to the Physical Sciences Self-Assessment: General

Chemistry Test. The goal of this test is to analyze your knowledge

in the content of the MCAT. In order to obtain an accurate

assessment of your strengths and weaknesses, you must answer

every question. Because the test is lengthy, you are encouraged to

take breaks as needed.

Good luck!

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Passage I

Ammonia is one of the most important chemicals

produced by the chemical industry. It is prepared by

the exothermic chemical reaction shown in reaction 1.

N2(g) + 3 H2(g) 2 NH3(g)

Reaction I

The conditions for Reaction 1 usually involve a

temperature of 450°C and a pressure of 320 atm.

Also, an iron catalyst is necessary to increase the rate

of the reaction.

Ammonia is separated from unreacted nitrogen

and hydrogen in the gaseous reaction mixture by

liquefying the ammonia. The separation is possible

because ammonia has a higher boiling point than

either nitrogen or hydrogen.

In the laboratory, ammonia is frequently used in

the form of its aqueous solution. Ammonia acts as a

weak base (Kb = 1.8 x 10–5

) in aqueous solutions, as

shown in reaction 2.

NH3 + H2O→ NH4+ + OH

–

Reaction II

The concentration of an aqueous solution of

ammonia can be determined by titrating a specific

volume of the ammonia solution with a standard

solution of a strong acid, such as hydrochloric acid.

As shown in Figure 1, 25.00 mL of an aqueous

solution of ammonia was titrated with a 0.10 M

solution of hydrochloric acid.

Figure 1

1. What is the percent, by mass, of nitrogen in NH3?

A ) 14%

B ) 25%

C ) 82%

D ) 97%

2. According to the Brønstead-Lowry acid-base

theory, which of the following species is the

conjugate acid of ammonia?

A ) H+

B ) H3O+

C ) NH3OH

D ) NH4+

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3. Which of the following acid-base indicators would

be best to use for determination of the equivalence

point for the titration shown in Figure 1?

A ) Thymol blue (pH range of color change is 1.2 to

2.8)

B ) Methyl red (pH range of color change is 4.2 to 6.3)

C ) Cresol red (pH range of color change is 7.2 to 8.8)

D ) Phenolphthalein (pH range of color change is 8.3

to 10.0)

4. Ammonia can act as a Lewis base because

ammonia:

A ) oxidizes water when it is in an aqueous solution.

B ) forms OH–ions in aqueous solutions.

C ) has a lone pair of electrons on the nitrogen atom.

D ) reacts with dilute hydrochloric acid.

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Passage II

Archaebacteria are often found in environments that

have extreme climatic conditions (e.g., in salt lakes or

in very acidic or alkaline hot springs). Most

archaebacteria are chemoautotrophs, bacteria that

obtain energy by a redox reaction. For example,

methanogens produce methane by metabolizing CO2.

The bond energy of C=O in CO2 is 803 kJ/mol, and

the C-H bond energy in CH4 is 414 kJ/mol.

Table 1 gives some of the chemical species that

scientists find in environments where archaebacteria

thrive.

Table 1 Chemicals

Name Formula

Methane CH4

Glycine H2N-CH2-COOH

Potassium hydroxide KOH

Sulfuric acid H2SO4

Carbon dioxide CO2

Methanol CH3OH

Sodium chloride NaCl

Hydrogen sulfide H2S

The methane found in swamp gas is a byproduct of

methanogens, which are also found in a symbiotic

association with a variety of cellulose-digesting

organisms, including cows and termites. Carbon-14

isotopic analysis even suggests that methane found

deep in the earth’s crust might have been produced by

archaebacteria.

5. Which of the following compounds has the same

geometry as methane?

A ) H2S

B ) CO2

C ) XeF4

D ) SiCl4

6. Like oxygen atoms in methanogens, which of the

following elements can act as an electron

acceptor?

A ) S

B ) He

C ) H2

D ) Fe

7. If an archaebacterial species lives in a pool that is

0.01 M HCl(aq), what is the pH of the water?

A ) 12

B ) 6

C ) 2

D ) 0.01

8. What pair of compounds found in Table 1 can

form extensive networks of intermolecular

hydrogen bonds with both participating?

A ) Methane and methanol

B ) Methane and glycine

C ) Glycine and methanol

D ) Methanol and carbon dioxide

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Passage III

Two different gases, Reactants X and Y, were

placed in either side of a reaction vessel that was

divided in half by a removable partition. The same

number of particles were placed in both sides of the

vessel.

The vessel temperature was equilibrated at 300 K,

and the partition was removed. The reactants mixed

and spontaneously reacted to form product molecules,

as shown in Figure 1.

Figure 1

When the experiment was repeated at 200 K, the

same amount of product was produced, but the

reaction proceeded more slowly than when it was run

at 300 K. When the procedure was repeated at 100 K,

no product was detected.

The activated energy, Ea, was determined to be 10

kJ/mole for this reaction.

9. Which of the following equations shows the net

reaction when the temperature was 300 K?

A ) X + Y2 → Y2X

B ) X +2Y → Y2X

C ) 2X + Y → YX2

D ) X2 + Y → YX2

10. Compared to the rate of the reaction between

Reactants X and Y at 300 K, the rate of the

reaction at 400 K would be:

A ) greater.

B ) the same.

C ) less.

D ) unrelated to the temperature.

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11. If the reaction between Reactants X and Y is

exothermic, which of the following diagrams

shows the energy profile of the reaction?

A )

B )

C )

D )

12. If Reactants X and Y are atoms, what is the shape

of the product molecules?

A ) Linear

B ) Bent

C ) Trigonal planar

D ) The shape of the product molecules cannot be

determined without more information.

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Passage IV

Hard water contains cations that form precipitates

with soap or upon boiling. The principal “hardness

ions” are Ca2+

, Mg2+

, and Fe2+

. There are 2 major

drawbacks associated with hard water.

First the X2+

ions reduce the effectiveness of

common soaps, which are sodium salts of organic

acids with long carbon chains. An example is sodium

stearate, C17H35CO2Na (MW = 306). The reaction

between soaps and the hardness ions yields insoluble

precipitates through the following reaction.

X2+

(aq) + 2 C17H35CO2Na (aq) → 2 Na+ (aq) +

X(C17H35CO2)2(s)

Reaction 1

Removal of stearate from the solution eliminates

the effectiveness of the soap.

Second, hard water produces boiler scale. The

hardness ions react with HCO3–, forming insoluble

carbonates that stick to the inner walls of pipes and

hot-water boilers.

X2+

(aq) + 2 HCO3–(aq) H2O(l) + CO2(g) +

XCO3(s)

Reaction 2

Deposits of this type are especially bad in hot water

and are poor conductors of heat.

It is important that the cations responsible for hard

water be removed before the water is heated or used

for washing. Water softening, the removal of the

hardness ions from water, can be accomplished in

several ways. One method is the ion-exchange

process, in which water is passed through a column

containing sodium aluminum silicates (zeolites). The

sodium ions of the zeolite are exchanged for the

hardness ions (Reaction 3), effectively removing them

from the water.

X2+

(aq) + 2 NaAlSi2O6(s) → 2 Na+(aq) +

X(AlSi2O6)2(s)

13. In some areas, residential hot-water heaters

should be cleaned periodically to remove:

A ) dissolved CO2 gas.

B ) insoluble aluminum silicates.

C ) insoluble stearate precipitates.

D ) insoluble carbonate deposits.

14. If reaction 2 is spontaneous and endothermic at

25° C, the:

A ) entropy change of the reaction must be positive.

B ) free energy change of the reaction equals zero.

C ) reaction generates excess heat.

D ) reaction is most likely nonspontaneous at 100°C.

15. Which of the following methods could be used to

regenerate a depleted zeolite ion-exchange

column?

A ) Washing the column with pure water

B ) Passing carbon dioxide gas through the dried

column

C ) Passing a sodium chloride solution through the

column

D ) Passing a calcium chloride solution through the

column

16. A sample of hard water contains 1 × 10–3

M Ca2+

ions and no other hardness ions. How many

grams of sodium stearate must be added to

remove all the CA2+

ions from 10 L of solution?

A ) [306 × 2 × 0.001 × 10] g

B ) [306 × 0.5 × 0.001 × 10] g

C ) [306 × 2 × 1,000 × 10] g

D ) [306 × 2 × 1,000 × 0.10] g

Reaction 3

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Passage V

The periodic table arranges the elements by atomic

number, aligning those with similar chemical

properties in columns. A primitive version of the

periodic table was created by a Russian chemist in

1869, long before the electronic configuration of the

elements was known. Dimitri Mendeleev grouped the

elements by their chemical properties and found that

the properties varied periodically with the atomic

mass. Mendeleev left empty spaces for undiscovered

elements. His genius was confirmed when the

elements that filled these blanks were isolated.

Henry Moseley showed that periodicity is a function

not of atomic mass but of atomic number, as stated by

today’s periodic law. The current periodic table

reflects this law. In 1985, an international committee

numbered the columns in the periodic table from 1 to

18 and abolished the A and B designations for main-

group and transition elements.

17. According to trends in electronegativity, which of

the following pairs of atoms is most likely to

form an ionic bond?

A ) N and O

B ) C and F

C ) Ca and I

D ) Si and Cl

18. Which of the following atoms has the largest

atomic radius?

A ) Sodium

B ) Aluminum

C ) Sulfur

D ) Chlorine

19. Which of the following atoms has the largest first

ionization energy?

A ) Potassium

B ) Zinc

C ) Gallium

D ) Krypton

20. What is the sum of the protons, neutrons, and

electrons in strontium–90?

A ) 90

B ) 126

C ) 128

D ) 218

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These questions are not based on a descriptive

passage and are independent of each other.

21. Which of the following elements has the highest

electron affinity?

A ) Carbon

B ) Fluorine

C ) Oxygen

D ) Magnesium

22. What is the conjugate base of the bisulfate ion

(HSO4–)?

A ) H+

B ) OH–

C ) SO42–

D ) H2SO4

23. Which of the following chemical species is NOT

isoelectronic with a neon atom?

A ) He

B ) F–

C ) Mg2+

D ) Na+

24. Which of the following is NOT characteristic of

ionic bond formation?

A ) It results from the electrostatic forces that exist

between particles of opposite charge.

B ) It occurs between 2 ions of very similar

electronegativity.

C ) It results from the net transfer of 1 or more

electrons from one atom to another.

D ) It results from the interaction of metals from the

left side of the periodic table with nonmetals from

the right side.

25. Which of the following describes the orbital

geometry of an sp3 hybridized atom?

A ) Linear

B ) Trigonal planar

C ) Tetrahedral

D ) Octahedral

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Passage VI

Olestra, a sucrose polyester, is the brand name of an

approved dietary fat replacement. The large-scale

synthesis of Olestra starts with a base-catalyzed

cleavage in methanol of the naturally occurring fats

(triacylglycerols or triglycerides) found in cottonseed

or soybean oils. The reaction liberates glycerine and

converts the fatty acids into methyl esters (Figure 1).

Figure 1 Base-catalyzed cleavage of a triacylglycerol

(R = CH3(CH2)n-; n = 8, 10, 12, etc.)

As glycerine settles out, a plant worker draws it off

and separates the methyl esters from the remaining

mixture by distillation. A reaction between these

esters and sucrose, common table sugar, in the

presence of a basic catalyst and emulsifiers at a high

temperature liberates methanol and produces crude

Olestra. The removal of excess fatty acids and

emulsifiers produces pure Olestra.

Normal edible fats contain three fatty acid units,

whereas Olestra, also a true fat, contains six to eight

fatty acid units bonded to the sugar backbone. Olestra

is not metabolized because the additional fatty acid

units block the approach of digestive enzymes to the

cleavage sites.

Because a calorie (1 cal = 4.185 J) is a very small unit

of energy, food scientists use the Calorie (1 Cal =

4,185 J) with a capital C. A 1-ounce bag of potato

chips contains about 160 Cal. A normal fat contains 9

Cal/g, whereas carbohydrates and proteins provide

about 4 Cal/g. (Note: For water, the heat of fusion is

1.4 kcal/mol, the specific heat is 4.185 J/g•oC or 1

cal/g•oC, and the density is 1.0 g/mL at 15

oC. One kg

equals 2.2 pounds.)

26. According to the passage, which of the following

compounds can the worker use to catalyze the

cleavage of a triglyceride?

A ) HCl(aq)

B ) NaCl(aq)

C ) NaOH(aq)

D ) Na2SO4(aq)

27. How many dietary calories does a 1-g sample of

Olestra contribute to a human consumer?

A ) 0 Cal

B ) 4 Cal

C ) 5 Cal

D ) 9 Cal

28. The boiling point of glycerine in comparison with

that of isopropyl alcohol, (CH3)2CHOH, is:

A ) more than 10oC higher.

B ) less than 10oC higher.

C ) less than 10oC lower.

D ) more than 10oC lower.

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29. What is the energy content in kcal of one peanut,

if the temperature of 1 kg of water in a

calorimeter increases by 50oC upon the

combustion of 10 peanuts?

A ) 0.5 kcal

B ) 1 kcal

C ) 5 kcal

D ) 10 kcal

Passage VII

Ammonia can be prepared by the reversible reaction between H2 and N2 in the presence of a mixture of FeO and

Al2K2O4 (Reaction 1) under a variety of conditions (Table 1).

Reaction 1

Table 1 Equilibrium Concentrations of NH3(g) at Several Temperatures and Pressures

Pressure

(atm)

Equilibrium concentration of NH3(g)

(% by volume)

at 200°C at 400°C at 600°C at 800°C

1 15.3 0.44 0.05 0.01

100 80.6 25.1 4.47 1.15

200 85.8 36.3 8.25 2.24

1,000 98.3 80.0 31.5 —

NH3 can also be prepared by reacting a metal nitride, such as Mg3N2, with H2O, as summarized by the following

unbalanced equation (Reaction 2).

Mg3N2(s) + H2O(l) → Mg(OH)2(s) + NH3(g)

Reaction 2

Ammonia and ammonium salts are used as commercial fertilizers. Ammonium salts are prepared by reacting NH3

with HX (an acid) as shown below (Reaction 3).

NH3(g) + HX(aq) → NH4X(s)

Reaction 3

The approximate electronegativities of several elements are given in Table 2.

Table 2 Electronegativities of Several Elements

Element Elecronegativity

H 2.20

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I 2.66

N 3.04

O 3.44

F 3.98

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30. Is Reaction 1 exothermic under standard

conditions?

A ) Yes, because heat must be added to initiate the

reaction

B ) Yes, because the standard enthalpy change is

negative

C ) No, because the percent yield of NH3 is greatest at

high pressure

D ) No, because the standard enthalpy change is

negative

31. The most likely role of the FeO/Al2K2O4 mixture

used in Reaction 1 is to:

A ) increase the rate of the reaction.

B ) increase the equilibrium constant.

C ) provide energy to facilitate the reaction.

D ) lower the pH of the reaction mixture.

32. What kind of interactions take place between

molecules of the product of Reaction 1?

A ) Ionic only

B ) Hydrogen bonding only

C ) Dipole-dipole only

D ) Both hydrogen bonding and dipole-dipole

33. Which of the following ions involved in Reaction

2 is the strongest base?

A ) N3–

(aq)

B ) OH–(aq)

C ) Mg2+

(aq)

D ) H+(aq)

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Passage VIII

Fertilizers are substances added to the soil to improve

plant growth and productivity. Commonly used

fertilizers contain ionic salts of N, P, and K. Because

of the complexity of soil chemistry, it is often

difficult to predict how soil pH will be affected by the

addition of a fertilizer.

Ionic salts used as fertilizers can generally be

classified chemically as either acidic or basic.

Ammonium dihydrogen phosphate (NH4H2PO4), a

commonly used fertilizer, can alter soil pH according

to Equation 1.

2 NH4H2PO4(s) 2 NH4+(aq) + H2PO4

–(aq) +

HPO42–

(aq) + H+(aq)

Equation 1

Alternatively, the fertilizer ammonium

monohydrogen phosphate [(NH4)2HPO4] can alter soil

pH according to Equation 2.

2 (NH4)2HPO4(s) + H2O(l) 4 NH4+(aq) +

HPO42–

(aq) + H2PO4–(aq) + OH

–(aq)

Equation 2

If a fertilizer alters the original soil pH too drastically,

CaCO3, a standard “liming” material, can be used to

raise soil pH, and CaCl2 can be used to lower soil pH.

Ammonia is sometimes applied directly to the soil to

increase the ammonium ion content by its interaction

with water in the soil. The ammonium ions from all

these sources can further affect soil pH during the

nitrification process. In this process, soil microbes

convert ammonium ions to nitrate ions according to

Equation 3.

NH4+(aq) + 2 O2(g) → NO3

–(aq) + H2O(l) + 2

H+(aq)

Equation 3

The nitrate ions are taken up by plants and converted

first to nitrite ions, NO2–, then to ammonia for amino

acid synthesis in the plant.

34. After adding the fertilizer shown in Equation 2 to

the soil, what will be the most likely effect of

excessively moist soil conditions?

A ) The degree of ionization will be greater, releasing

more OH–.

B ) The degree of ionization will be greater,

consuming more OH–.

C ) The degree of ionization will be reduced, releasing

more OH–.

D ) The degree of ionization will be reduced,

consuming more OH–.

35. Which of the following is the most likely reason

that plants CANNOT utilize nitrogen from the

atmosphere?

A ) N2 is present in very low concentrations in the

atmosphere.

B ) N2 is too polar.

C ) N2 is very unreactive because it is a noble gas.

D ) N2 is very unreactive because of the great strength

of the N≡N triple bond.

36. In Equation 1, HPO42–

is the conjugate:

A ) acid of NH4+.

B ) base of NH4+.

C ) acid of H2PO4–.

D ) base of H2PO4–.

37. In the equilibrium constant expression for

Equation 2, [H2O] is omitted because the salt is:

A ) only weakly basic, and [H2O] is nearly constant.

B ) strongly basic, and [H2O] is nearly zero.

C ) only weakly acidic, and [H2O] is nearly constant.

D ) strongly acidic, and [H2O] is nearly zero.

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Passage IX

The figure below illustrates an experiment

designed to relate the heat generated in a resistor due

to the current passing through the resistor and the

potential difference across it. The resistor is a coil of

electrically insulated copper wire with a resistance of

10 Ω. It is immersed in a 500-g oil bath contained in a

double-walled calorimeter that is thermally isolated

from the external environment. The oil has a specific

heat of 2.93 J/g °C at an initial temperature of 20° C.

The oil bath is stirred continually by a slowly rotating

fan blade on a thermally insulated shaft, and the

temperature is recorded at 100-sec intervals.

The heat capacity of the thermometer is 12.6 J/°C;

and that of the stirrer, inner cup, and resistor

combined is 24.2 J/°C. The walls of the inner and

outer calorimeter cups are highly polished, and the

cover forms an airtight seal with each cup. The space

between the cups is evacuated before the start of the

experiment, as is the space above the oil bath. The

electrical power is supplied by a 12-V storage battery

with negligible internal resistance. A voltmeter, RINT

= 106 Ω, and an ammeter, RINT = 1 Ω, are connected

as shown to measure potential difference and current,

respectively.

38. In the absence of stirring, as current passes

through the resistor and the adjacent oil is heated,

how will that oil’s density and position change?

A ) The heated oil should decrease in density and rise.

B ) The heated oil should decrease in density and sink.

C ) The heated oil should increase in density and rise.

D ) The heated oil should increase in density and sink

39. The connecting wires on the resistor are made of

insulated copper and are highly flexible. In order

for the resistor to remain immersed in the bath,

the oil must have a lower:

A ) density than the insulated copper wire.

B ) thermal conductivity than air.

C ) electrical conductivity than copper.

D ) melting point than water.

40. The space between the cups is evacuated before

the experiment to prevent:

A ) combustion of the oil.

B ) conductive heat loss.

C ) radiative heat loss.

D ) contamination of the oil.

41. As the experiment proceeds, the pressure of the

oil vapor above the bath increases. One reason is

the increasing number of molecules in the vapor.

Which of the following is another reason?

A ) Increasing volume of the vapor

B ) Decreasing molecular kinetic energies

C ) Heat of vaporization released

D ) Increasing temperature of the vapor

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Passage X

Coulometric methods offer a means of monitoring

gases. For example, Figure 1 shows a schematic

diagram of an apparatus that can be used to determine

ultrasmall concentrations of oxygen.

Figure 1 Coulometric determination of oxygen

concentration

The oxygen is bubbled over a silver electrode where it

is reduced according to the reactions represented by

Equations 1 and 2. The electrochemical reaction is

completed at the cadmium electrode. The half

reaction is given by Equation 3.

O2(g) + 2H2O + 4e–

4OH– Ε

o = +0.40 V

Equation 1

Ag+ + e

– Ag(s) Ε

o = +0.80 V

Equation 2

Cd(s) + 2OH–

Cd(OH)2(s) + 2e– Ε

o = +0.81 V

Equation 3

The current produced is measured by recording the

potential drop as it passes through a standard resistor

(R). The oxygen concentration is proportional to the

potential.

The procedure is reported to be accurate over a range

from 1 ppm up to 1% of the gas stream. The accuracy

of the procedure depends on an adequate flow rate.

42. How many ppm is 1%?

A ) 100

B ) 1,000

C ) 10,000

D ) 100,000

43. How is the accuracy of the oxygen determination

affected by the addition of a gas into the stream

that is reduced by a reaction analogous to that of

oxygen?

A ) Increased, because the smaller the amount of

oxygen in the stream, the more effective is

microanalysis

B ) Increased, because the larger the sample reduced,

the less effect a small variation in measurement

will have on results

C ) Decreased, because the partial pressure of oxygen

will be decreased

D ) Decreased, because the method cannot distinguish

oxygen from the added gas

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44. Would methane gas (CH4) be a candidate for

determination by the method described in the

passage?

A ) Yes, because carbon, like oxygen, is a nonmetal

B ) Yes, because carbon, like oxygen, is in the 2nd

period of the periodic table

C ) No, because hydrogen is already at its lowest

oxidation state in methane

D ) No, because carbon is already at its lowest

oxidation state in methane

45. In the schematic diagram shown in Figure 1, the

Cd electrode is:

A ) the anode, because oxygen gas is reduced there.

B ) the anode, because the silver electrode is where

reduction occurs.

C ) the cathode, because the silver electrode is where

reduction occurs.

D ) the cathode, because the silver electrode is where

oxidation occurs.

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46. Which of the following valence electron

configurations corresponds to an atom in an

excited state?

A ) 1s22s

2

B ) 2s22p

1

C ) 3s23d

1

D ) 4s23d

2

47. Which one of the following general

characteristics is shared by all catalysts?

A ) They induce more collisions among reactant

molecules.

B ) They transfer kinetic energy to the reactant

molecules.

C ) They increase the reaction rate but do not change

the Keq of a reversible reaction.

D ) They increase both the reaction rate and the Keq of

a reversible reaction.

48. Gas X has a density of 1.44 g/L and gas Y has a

density of 1.54 g/L. Which gas diffuses faster?

A ) Gas X, because it has a lower molar mass than gas

Y

B ) Gas X, because it has a higher molar mass than gas

Y

C ) Gas Y, because it has a lower molar mass than gas

X

D ) Gas Y, because it has a higher molar mass than

gas X

49. What is the pH of a .001 M NaOH solution?

A ) .001

B ) 3

C ) 7

D ) 11

50. A reaction is designed to produce ammonia from

the gas phase equilibrium of nitrogen and

hydrogen.

N2(g) + 3 H2(g) 2 NH3(g)

Introducing a catalyst into the system will cause

the amount of ammonia at equilibrium:

A ) to increase.

B ) to remain the same.

C ) to decrease.

D ) to change in a manner which depends on the value

of the equilibrium constant.

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Passage XI

The following experiments study the reactivities of

several active metals (Experiment 1) and halogens

(Experiment 2).

Experiment 1

Pea-sized samples of five active metals were placed

in deionized water, and observations were recorded in

Table 1.

Table 1 Observations

Metal

used

Observation upon

adding the metal to

water

Observation of

the resulting

solution

Mg No obvious reaction Neutral

Ca Sank, and slowly gave

off bubbles of a gas

Basic

Li Moved over the surface

slowly fizzing

Basic

Na Moved over the surface

vigorously fizzing,

caught fire

Basic

K Moved over the surface

vigorously fizzing,

exploded loudly

Basic

Experiment 2

A saturated aqueous solution of Cl2 was added to

separate aqueous solutions of NaF, NaCl, NaBr, and

NaI and mixed well. Observations were recorded. In

addition, samples of salt solutions were added to

separate electrolysis cells, and the minimum voltage

required to produce an observable reaction at the

anode was recorded. H2(g) was produced at the

cathode in each cell and, except for the NaF solution,

the solutions became basic. Results are recorded in

Table 2.

Table 2 Results

Solution Chlorine water

Electrolysis cell

voltage and product

NaF No change 2.06 V; O2(g)

NaCl No change 2.19 V; Cl2(g)

NaBr Red-brown 1.90 V; Br2(aq)

NaI Yellow-brown 1.37 V; I2(aq)

51. The process taking place at the cathode was:

A ) oxidation by a loss of electrons.

B ) oxidation by a gain of electrons.

C ) reduction by a loss of electrons.

D ) reduction by a gain of electrons.

52. Which of the following properties is most useful

in explaining the trend in the reactivities in

Experiment 1?

A ) Electronegativity

B ) Ionization potential

C ) Electron affinity

D ) Polarizability

53. Experiment 1 was repeated with 0.40 g of

calcium, and the gas that evolved was collected.

The identity of the gas, and its approximate

volume at 1.0 atm and 27°C were:

(Note: R = 0.0821 L•atm/mol•K)

A ) H2, 250 mL.

B ) H2, 500 mL.

C ) O2, 250 mL.

D ) O2, 500 mL.

54. What is the electron configuration of the metal

ion produced when Ca reacted with water in

Experiment 1?

A ) 1s22s

22p

63s

23p

64s

2

B ) 1s22s

22p

63s

23p

64s

1

C ) 1s22s

22p

63s

23p

6

D ) 1s22s

22p

63s

23p

64s

23d

2

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Passage XII

In 1622, a Spanish ship carrying a cargo of silver

crashed on a coral reef near Cuba and sank. The ship

was laden with hardwood boxes of silver coins. The

boxes came to rest on the ocean floor and began to

decay. At first, aerobic microorganisms thrived but,

as the concentration of oxygen decreased, these

organisms died. Subsequently, sulfur-loving bacteria

began to flourish.

These sulfur bacteria consumed sulfate ions in

seawater and excreted the weak acid H2S, as shown in

Equation 1.

SO42–

(aq) + 2 H+(aq) + 4 H2(g) → H2S(aq) + 4

H2O(l)

Equation 1

The excreted H2S then reacted with silver, which has

a standard reduction potential of +0.80 V. One of the

products was a black precipitate of Ag2S and the other

was hydrogen gas, as shown in Equation 2.

2 Ag(s) + H2S(aq) → Ag2S(s) + H2(g)

Equation 2

The hydrogen from this reaction provided additional

food for the sulfur microorganisms and accelerated

the corrosion of the silver coins. When the silver

coins were completely coated with Ag2S, the

corrosive reaction stopped.

Because the seawater contained small amounts of

CO2 (the solubility of CO2 is 0.145 g/100 g H2O at

25oC and 1.00 atm), bicarbonate ions were formed by

the reaction shown in Equation 3.

H2O(l) + CO2(g) H+(aq) + HCO3

–(aq)

Equation 3

These bicarbonate ions combined with calcium to

form the insoluble CaCO3, which crystallized,

encapsulating the coins, sand, and decaying matter

into rock-like clumps. The explorers who discovered

the treasure found these rock-like structures.

55. What is the maximum number of grams of H2S

that can be produced from 2 mol of sulfate ions

by the reaction of Equation 1?

A ) 68 g

B ) 34 g

C ) 96 g

D ) 192 g

56. The formation of Ag2S is an example of what

kind of reaction?

A ) A combination reaction

B ) A decomposition reaction

C ) A single replacement reaction

D ) A double replacement reaction

57. What species is the reducing agent in Equation 2?

A ) S2–

B ) H2S

C ) H+

D ) Ag

58. To a first approximation, the ionization constant

of H2S is:

A ) near zero.

B ) much less than 1.

C ) about 1.

D ) much more than 1.

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Passage XIII

The interaction between metals and hydrocarbons

is important in both biological and industrial

catalysis. Researchers are probing the fundamental

chemistry of these interactions by measuring the gas-

phase reactivity of transition-metal atoms with

hydrocarbons. In a typical reaction, metal atoms are

introduced into a helium buffer gas at the head of a

73-cm fast-flow tube. Table 1 shows the initial helium

and metal gas-flow conditions.

Table 1 Initial Flow Conditions

Pressure

(torr)

Mole fraction

He

Metal velocity

(cm s–1

)

0.5 0.93 8160

0.8 0.96 9070

1.1 0.98 9420

A large excess of a hydrocarbon gas such as

ethene is then injected into the metal gas stream, and

the rate of the reaction is measured by monitoring the

concentration of unreacted metal versus reaction time

(distance/velocity).

Equation 1 shows a proposed one-step reaction

mechanism for the reaction of a metal (M) with a

hydrocarbon (HC).

M(g) + HC(g) product

Equation 1

If the HC(g) is in a large excess, its concentration

is considered to be constant, and the rate expression

shown in Equation 2 is obtained, in which [M] is the

concentration of metal at time t, and k and k1 are rate

constants.

ln [M/Mo] = –k1[HC]t = –kt

Equation 2

Several rate constants reported for metal reactions

with ethene at 298 K are shown in Table 2 (NR = no

reaction). The researchers suggest that two effects

involving metal orbitals influence the reaction rate. A

full valence s subshell hinders reaction, and valence s

and d orbitals of similar energy form sd hybrid

orbitals, enhancing the reaction.

Table 2 Rate Constants, k (10–12

cm3 s

–1), at Three

Pressures

Pressure (torr)

Pressure (torr)

Metal 0.5 0.8 1.1 Metal 0.5 0.8 1.1

Ti — NR — Ni — 0.5 —

Zr — 59 28 Pd — 15 —

Hf 29 28 28 Pt 387 376 351

V — NR — Cu — NR —

Nb — 314 — Ag — NR —

Ta 9.6 8.4 — Au — NR —

59. The metals shown in Table 2 belong to which

block of elements in the periodic table?

A ) s

B ) p

C ) d

D ) f

60. According to Table 2 and information in the

passage, the reactivity of platinum (5d96s

1)

relative to gold (5d10

6s1) is attributable to the

metal–HC interaction, which involves:

A ) only valence s electrons.

B ) sd hybrid orbitals.

C ) sp hybrid orbitals.

D ) only valence d electrons.

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61. 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

.)

A ) [(1.1)(π)(1)2(0.98)]/[(1000)(760)(0.082)(298)]

B ) [(1.1)(π)(1)(73)2(0.98)]/[(1000)(760)(0.082)(298)]

C )

[(1.1)(π)(2)2(73)(0.98)(4.0)]/[(1000)(760)(0.082)(2

98)]

D ) [(1.1)(π)(1)2(73)(0.98)]/[(1000)(760)(0.082)(298)]

62. What does a nonlinear plot of ln [M] versus t

indicate about the concentration of the

hydrocarbon (HC) and the reaction mechanism?

A ) The HC is not in excess, and the mechanism is

M + heat M* (fast)

M* + HC product (slow)

B ) The HC is in excess, and the mechanism is

M + heat M* (fast)

M* + HC product (slow)

C ) The HC is not in excess, and the mechanism is

M + heat M* (slow)

M* + HC product (fast)

D ) The HC is in excess, and the mechanism is

M + heat M* (slow)

M* + HC product (fast)

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Passage XIV

A class was studying electrochemistry. The instructor

gave each student an unknown. Some of the data are

shown in Table 1.

Table 1 Student Data

Student Nature of unknown Measurement

1 0.01 M monoprotic acid pH = 4.0

2 0.001 M monoprotic acid pH = 3.0

3 1.0 M cation Εo = 1.10 V

4 White solid (58.5 g/mol) –

5 Solution of Fe2(SO4)3 –

Some students required the Nernst equation, Equation

1.

Εcell = Εocell– (0.0592/n)log10(Q)

Equation 1

In Equation 1, n equals the number of moles of

electrons transferred in the redox reaction, and Q is

the reaction quotient. The expression for Q in terms

of concentrations of reactants and products is written

in the same manner as is the expression for the

equilibrium constant, Keq, for a reaction. The standard

cell potential Εocell (in volts) of a galvanic cell is

obtained when all the components of the cell are in

their standard (thermodynamic) states. Thus, Εcell

equals zero, when Q equals Keq.

All of the students studied the reaction given by

Equation 2 (unbalanced), for which Εocell= 0.32 V.

MnO4–(aq) + H

+(aq) + ClO3

–(aq) → ClO4

–(aq) +

Mn2+

(aq) + H2O(ℓ)

Equation 2 (unbalanced)

Standard reduction potentials for certain electrodes

are given in Table 2.

Table 2 Standard Reduction Potentials

Half-reaction Εo, Volts

Ag+(aq) + e

– → Ag(s) +0.80

Cu2+

(aq) + 2e– → Cu(s) +0.34

2H+(aq) + 2e

– → H2(g) 0.00

Zn2+

(aq) + 2e– → Zn(s) –0.76

Al3+

(aq) + 3e– → Al(s) –1.66

Ca2+

(aq) + 2e– → Ca(s) –2.76

63. If Student 3’s measurement (Table 1) was

obtained from a cell made by connecting the

unknown solution to a standard zinc electrode

(Table 2) by means of a salt bridge, which of the

following ions was Student 3’s unknown?

A ) Ag+

B ) Cu2+

C ) Al3+

D ) Ca2+

64. If Student 4 prepared a solution by dissolving

29.25 g of the assigned unknown in water to a

total volume of 250.0 mL, the molarity of the

solution was:

A ) 0.250 M.

B ) 0.500 M.

C ) 1.00 M.

D ) 2.00 M.

65. The name of Student 5’s unknown is:

A ) iron(II) sulfate.

B ) iron(II) sulfite.

C ) iron(III) sulfate.

D ) iron(III) sulfite.

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66. Which expression gives the reaction quotient for

a spontaneous reaction between standard silver

and aluminum electrodes (Table 2)?

A ) [Al3+

][Ag+]

B ) [Al3+

]/[Ag+]3

C ) [Ag+]

3/[Al

3+]

D ) [Al3+

][Ag(s)]3/[Ag

+]

3[Al(s)]

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Passage XV

At the critical point, the density of liquid CO2 is equal

to the density of gaseous CO2. This occurs at specific

conditions of temperature and pressure. At

temperatures and pressures above the critical point

values, CO2 is deemed supercritical. For a

supercritical fluid, the density and ability to dissolve

other substances are similar to values expected for

liquids. The following figures give phase data for

CO2.

Figure 1 Phase diagram for CO2

Figure 2 Isothermal curves for CO2 near the critical

point. V (× 104) is relative to V = 1.000 at 0

oC and

1.000 atm.

67. In Figure 2, which of the points (A-D) is the

critical point for CO2?

A ) A

B ) B

C ) C

D ) D

68. Which of the following compounds is most

soluble in supercritical CO2?

A ) NaCl

B ) C2H5OC2H5

C ) NH4NO3

D ) KOH

69. Water is a liquid at room temperature, yet CO2 at

room temperature is liquid only at high

pressures. Which of the following best explains

this?

A ) CO2 is polar and has strong intermolecular forces.

B ) CO2 is nonpolar and has strong intermolecular

forces.

C ) CO2 is polar and has weak intermolecular forces.

D ) CO2 is nonpolar and has weak intermolecular

forces.

70. According to Figure 1, what is the critical

temperature and pressure of CO2?

A ) –56.1oC and 6.0 atm

B ) –54.1oC and 119.0 atm

C ) 31.1oC and 75.3 atm

D ) 25.0oC and 1.0 atm

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71. Which of the following substances is NOT a

base?

A ) NH3

B ) SO42–

C ) NH4+

D ) Fe(OH)2

72. Consider the following equilibrium in a closed

system.

N2O4(g) 2 NO2(g) ΔH° = 58.0 kJ

Which of the following will favor the formation

of N2O4

A ) Decreasing the temperature

B ) Decreasing the concentration of NO2

C ) Decreasing the pressure at constant temperature

D ) Increasing the volume

73. Which of the following titration curves best

represents the titration of a strong acid with .10

M NaOH?

A )

B )

C )

D )

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74. Ag+

+ e– → Ag E

o = +0.80 V

Cu+

+ e– → Cu E

o = +0.52 V

Pb2+

+ 2 e– → Pb E

o = –0.13 V

Zn2+

+ 2 e– → Zn E

o = –0.76 V

With which of the above metals can copper form

a galvanic cell in which copper is reduced?

A ) With silver only

B ) With lead only

C ) With lead and zinc

D ) With silver and zinc

75. Which of the following substances is most likely

to be more soluble in 1.0 M HCl than in 1.0 M

NaOH?

A ) AgCl

B ) Pb(OH)2

C ) CaF2

D ) HI

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Passage XVI

A chemist measured some physical properties of an

unknown element (X) and its oxide. The results are

summarized in Table 1.

Table 1 Physical Properties of Element X and Its

Oxide

Element X Oxide of

X

Density (g/cm3) 1.54 3.30

Melting point (oC) 839 2614

Boiling point (oC) 1484 2850

Solubility (g/100 g H2O at

25oC)

not

measured

0.12

The chemist concluded that the oxide was an ionic

compound because of its high melting and boiling

points. When the solubility experiment was

conducted, the element reacted with water at room

temperature and liberated a flammable gas.

Dissolution of the oxide in water produced a pH

greater than 7. The boiling point of the oxide solution

was slightly higher than 100oC.

The emission spectrum of element X displayed a

number of lines in the visible region; the red

emissions were particularly intense. The chemist

compared certain properties of the unknown with

those of oxygen. The data are shown in Table 2.

Table 2 Properties of Element X and Oxygen

Element

X

Oxygen

Electronegativity 1.0 3.5

First ionization energy

(kJ/mol)

590 1300

Second ionization energy

(kJ/mol)

1100 3400

Third ionization energy

(kJ/mol)

4912 5300

76. What is the physical state of the unknown

element X at 1200oC?

A ) Solid

B ) Liquid

C ) Gas

D ) Plasma

77. According to data presented in the passage,

which of the following charge distributions best

describes the oxide of element X?

A ) Element X positive, oxygen positive

B ) Element X positive, oxygen negative

C ) Element X negative, oxygen positive

D ) Element X negative, oxygen negative

78. The gas that evolved when the chemist tried to

dissolve element X was most likely:

A ) water vapor produced from the heat of reaction.

B ) oxygen produced by chemical reaction.

C ) hydrogen produced by chemical reaction.

D ) nitrogen that had been dissolved in the water from

air.

79. According to the ionization energies shown in

Table 2, element X is:

A ) an alkali metal.

B ) an alkaline earth metal.

C ) a transition metal.

D ) a nonmetal.

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Passage XVII

Although normal rainfall has a pH of about 5.6, in

highly industrialized areas, pH values of 3 or lower

have been measured. Acid rain has an average pH of

about 4.4.

Rainwater becomes acidic when it reacts with the

oxides of nitrogen and sulfur, which are produced

during the combustion of fossil fuels. The primary

contributor to acid rain is SO2, which is oxidized in

air to SO3. The SO3 may then combine with airborne

water droplets to form sulfuric acid. Acid rain

dissolves CaCO3, the main component in marble,

according to the following reaction.

H2SO4 + CaCO3 → CaSO4 + H2O + CO2

Below a pH of 4, the rate of dissolution is

proportional to the H+ concentration. Between pH

values of 4 and 6, the dissolution becomes less

dependent on the concentration of H+ and more

dependent on water flow and CO2 pressure. Above a

pH of 6, the dissolution of CaCO3 is independent of

the hydrogen ion concentration.

80. Based on the pKa values given below, which of

the following species is the strongest Brønstead

base?

HCl: pKa = –7.0

HNO3: pKa = –1.3

HCN: pKa = 9.2

A ) H+

B ) Cl–

C ) NO3–

D ) CN–

81. The pH of acid rain found in industrialized areas

would increase if the release to the atmosphere of

which of the following were decreased?

I. SO2

II. CaO

III. N2

IV. NO

A ) I and IV only

B ) II and III only

C ) I, II, and IV only

D ) I, II, III and IV

82. Limestone, marble, chalk, and Iceland spar are all

composed of CaCO3 crystals. Which of the

following could cause the differences in the

properties of the materials?

I. Crystal grain size

II. Conditions of formation

III. Molecular formula

IV. Impurities

A ) I and III only

B ) I, II, and IV only

C ) II, III, and IV only

D ) I, II, III, and IV

83. The solubility of calcium sulfate would be

expected to be low in water because:

A ) SO42–

is polyatomic.

B ) oxygen atoms are highly electromagnetic.

C ) both ions are highly charged.

D ) calcium ions are small compared to neutral

calcium atoms.

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Passage XVIII

Inorganic compounds with ring systems that contain alternating boron (B) and phosphorus (P) atoms can be

synthesized under anhydrous conditions. Figure 1 shows the structures of compounds 1 and 2.

Figure 1 Compounds 1 and 2 (R = isopropyl = iso-C3H7)

Equations 1a and 1b show the synthesis of Compound 1, which contains a four-membered ring, and Equation 2

shows the synthesis of Compound 2, which contains a six-membered ring.

2 R2NBCl2 + 5 LiPH2 → 4 LiCl + 3 PH3 + Intermediate

Equation 1a

Intermediate + HCl → LiCl + Compound 1

Equation 1b

3 R2NBCl2 + 6 LiPH2 → 6 LiCl + 3 PH3 + Compound 2

Equation 2

Table 1 shows structural data for compounds 1 and 2.

Table 1 Structural Data for Compounds 1 and 2

Compound

Average

B-P bond

length

(pm)

Average

B-N bond

length

(pm)

Ring

geometry

Geometry

of

boron

Geometry

of

phosphorus

1 193 138 Planar Trigonal

planar

Trigonal

pyramidal

2 194 139 Puckered Trigonal

planar

Trigonal

pyramidal

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Table 2 shows how bond length varies with bond order for both boron-phosphorus (B-P) and boron-nitrogen (B-

N) bonds. The data come from experimental studies, as well as theoretical calculations on the hypothetical

molecules H2BPH2 and HBPH.

Table 2 Bond Order versus Bond Length

B-P

Bond order

B-P

Bond length

(pm)

B-N

Bond order

B-N

Bond length

(pm)

1.0 190 1.0 142

2.0 181 2.0 130

3.0 165 – –

84. Phosphine (PH3) has which of the following

Lewis structures?

A )

B )

C )

D )

85. What formula is the same for compounds 1 and

2?

A ) Valence-bond

B ) Empirical

C ) Molecular

D ) Structural

86. What is the maximum volume of PH3(g) that a

chemist can obtain from the reaction shown by

Equation 1a, if 0.005 mol LiPH2 reacts with 0.002

mol R2NBCl2 at 0oC and 1 atm?

A ) 0.672 mL

B ) 6.72 mL

C ) 67.2 mL

D ) 67.2 L

87.

The above plot shows how the volume of a 1.0-g

sample of Compound 1 in the gaseous state varies

with temperature at constant pressure. Where on

the graphic would a similar plot of a 1.0-g sample

of Compound 2 appear?

A ) Below the plot for Compound 1

B ) Above the plot for Compound 1

C ) Precisely on top of the plot for Compound 1

D ) Intersecting the plot for Compound 1 at its

midpoint with an opposite slope.

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Passage XIX

The hardness of water is caused by the presence of

calcium and other ions that form insoluble

compounds with ordinary soap. Ground water in

limestone regions may contain a large amount of

calcium as CaCO3. The high degree of solubility of

CaCO3 in acidic solutions (due to conversion to

soluble Ca(HCO3)2) is responsible for water hardness

in these regions.

One way to soften acidic groundwater is by simply

boiling, which results in the removal of calcium ion

by Reaction 1.

Ca2+

+ 2HCO3– CaCO3(s) + H2O + CO2(g)

Reaction 1

The precipitated calcium carbonate is then removed

by filtration.

An alternative method of achieving the same result is

to add calcium hydroxide to the water sample, which

allows removal of calcium carbonate by Reaction 2.

Ca2+

+ 2HCO3– + Ca(OH)2(aq) 2CaCO3(s) +

2H2O

Reaction 2

This method is a more economical means of reducing

the water hardness on a large scale because of the

large fuel cost of boiling.

88. How many grams of CaCO3 would be formed in

Reaction 1 if the CO2 evolved occupies 11.2 L at

STP?

A ) 0.5 g

B ) 11.2 g

C ) 50 g

D ) 100 g

89. Reaction 1 is an effective means of decreasing

the hardness of an acidic water sample because it:

A ) increases the pH and decreases the solubility of

CaCO3.

B ) decreases the pH and decreases the solubility of

CaCO3.

C ) increases the pH and converts HCO3– to water.

D ) decreases the pH and removes Ca2+

from solution.

90. What is the effect of a high level of atmospheric

CO2 on the hardness of water in limestone

regions?

A ) It would lower the pH and increase the solubility

of CaCO3.

B ) It would raise the pH and increase the solubility of

CaCO3.

C ) It would lower the pH and decrease the solubility

of CaCO3.

D ) It would raise the pH and decrease the solubility of

CaCO3.

91. The addition of excess Ca2+

to a solution

containing Ca2+

and CO32–

ions causes CaCO3 to

precipitate because:

A ) Ksp for CaCO3 would increase due to the increase

in [Ca2+

].

B ) Ksp for CaCO3 would decrease due to the increase

in [Ca2+

].

C ) the reactivity quotient Q would be lower than Ksp.

D ) the reactivity quotient Q would be greater than

Ksp.

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Passage XX

Unlike most other substances, water is less dense in its solid phase than in its liquid phase. Also, the density

of the liquid phase of water is greatest at approximately 4° C.

One explanation for the unusual density of water is that ordered clusters of water molecules exist in ice and

in the liquid phase below 4° C. When the ordered structure of ice is broken, water molecules may move closer

together, filling in the gaps that are present in ice. The density of water will therefore increase as the

temperature is raised from 0° C to 4°C. The density of water decreases at temperatures above 4° C. A

representation of the structure is shown in Figure 1.

Figure 1

Water in lakes, streams, and oceans contains a variety of impurities and therefore will rarely freeze at 0° C

or boil at 100° C. This behavior is due to the freezing-point depression (Kf = 1.86° C/m) and boiling-point

elevation (Kb = 0.52° C/m) of water.

The freezing-point depression of seawater may be explained by examining vapor pressure of seawater as

compared to pure, deionized water. Figure 2 shows the vapor pressures plotted against temperature.

Figure 2

In Figure 2, Point B is the freezing point of pure, deionized water; Point A represents the freezing point of

seawater. When seawater freezes slowly, its vapor pressure is the same as that of pure ice at that temperature.

This indicates that the ice that freezes from seawater is free of the impurities in the water. However, the

concentration of the impurities in the ice depends on the rate of freezing.

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Density of seawater: 1.025 g/mL

Heat capacity of water: 75.3 J/mole.K

Heat of fusion of water: 6,020 kJ/mole

Molalities of the 5

ions in the greatest

abundance in seawater:

Na+ (0.470 m)

K+ (0.010 m)

Ca2+

(0.010 m)

Mg2+

(0.054 m)

Cl– (0.598 m)

92. Ice that slowly forms from seawater will have a

sodium ion concentration:

A ) close to zero.

B ) greater than that of seawater.

C ) equal to that of seawater.

D ) less than that of pure water.

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93. Based on the information given in the passage,

which will have a higher boiling point: 1 m

glucose or seawater?

A ) Seawater, because the total molality of seawater is

greater than 1 m glucose

B ) Seawater, because glucose has a larger molecular

weight than the ions in seawater

C ) 1 m glucose, because glucose solutions are not

ionic

D ) 1 m glucose, because the total molality of 1 m

glucose is less than seawater

94. Which of the following graphs best represents a

plot of the vapor pressure of seawater and pure

water near their respective boiling points? (Note:

Point C is the boiling point of pure water; Point D

is the boiling point of seawater.)

A )

B )

C )

D )

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95. Based only on the information in the passage,

which of the following expressions should be

used to best estimate the temperature (°C) at

which ice will form in seawater?

A ) 0 – 1.86(6.020)

B ) 0 – 1.86(1.025)

C ) 0 – 1.86(4.184)

D ) 0 – 1.86(1.142)

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Passage XXI

Metals can occur as free elements or in

compounds as ions with positive oxidation states. The

more active a metal is, the more difficult it is to

reduce it to a free element. Table 1 shows the

standard reduction potentials for several common

metals and hydrogen.

Table 1

Half-reaction E° (V)

Na+(aq) + e

– → Na(s) –2.71

Mg2+

(aq) + 2 e– → Mg(s) –2.37

Zn2+

(aq) + 2 e– → Zn(s) –0.76

Ni2+

(aq) + 2 e– → Ni(s) –0.25

Pb2+

(aq) + 2e– → Pb(s) –0.13

2 H+(aq) + 2 e

– → H2(g) 0.00

Cu2+

(aq) + 2e–

→ Cu(s) +0.34

Ag+(aq) + e

– → Ag(s) +0.80

Au3+

(aq) + 3 e– → Au(s) +1.50

Some metal ions exist in only 1 oxidation state

and are colorless in solution. Transition metals often

form ions of several oxidation states that are colored

in solution.

Transition metals frequently form complexes

consisting of a central metal cation and several anions

and/or charged or uncharged species called ligands.

Ligands form coordinate covalent bonds with the

central cation in complexes. The coordination

complex ion, [Co(NH3)4Cl2]+, consists of Co

3+, 4 NH3

ligands, and 2 Cl– ligands.

96. Based on the oxidation states of the ions in Table

1, how many moles of copper will be oxidized

when 1 mole of gold ions is reduced to the

elemental form in a galvanic cell?

A )

B )

C ) 2

D ) 3

97. Which of the following causes some metal ions to

have color when in solution?

A ) The hydrolysis reaction of the ion with water

B ) The loss of d-electrons during ionization

C ) The transition energies of d-electrons

D ) The shielding of electrons in lower shells by d-

orbital electrons

98. What is the standard cell potential (E°) for the

galvanic cell formed with Zn(s)/Zn2+

(aq) and

Ag(s)/Ag+(aq) half-cells?

A ) –2.36 V

B ) +0.04 V

C ) +1.56 V

D ) +2.36 V

99. Which of the following species would reduce a

1.0 M solution of Pb2+

to Pb(s)?

A ) Mg

B ) Cu

C ) Na+ in a 1.0 M solution

D ) Au3+

in a 1.0 M solution

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These questions are not based on a descriptive passage and are independent of each other.

100. As atomic number increases in a horizontal row of the periodic table, ionization energy generally:

A ) increases, because of increasing effective nuclear charge.

B ) increases, because of increasing atomic radius.

C ) decreases, because of decreasing effective nuclear charge.

D ) decreases, because of increasing atomic radius.

101. Based on the table below, which of the following species is the strongest oxidizing agent?

Half-reaction

Standard

potential

(V)

Na(s) → Na+(aq) + e

– 2.71

MnO4–(aq) + 8 H

+(aq) + 5 e

– → Mn

2+(aq) + 4 H2O(l) 1.51

I2(s) + 2 e– → 2 I

–(aq) 0.54

Ni(s) → Ni2+

(aq) + 2 e– 0.28

A ) Na+

B ) MnO4–

C ) I2

D ) Ni2+

102. An electrochemical cell is designed to produce pure copper from CuSO4. An increase in which of the

following cell conditions will most effectively increase the rate at which pure copper is produced?

A ) The concentration of SO42+

(aq)

B ) The current of electricity

C ) The size of the cathode

D ) The size of the anode

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103. The following data were collected for the reaction A + B → C.

Exp

Concentration

of A

(M)

Concentration

of B

(M)

Initial rate

of reaction

(M/sec)

1 0.100 0.100 3 × 10–5

2 0.100 0.200 3 × 10–5

3 0.200 0.100 12 × 10–5

What is the rate law for the reaction?

A ) Rate = k[A]2

B ) Rate = k[B]2

C ) Rate = k[A][B]

D ) Rate = k[A]2[B]

104. What is the molar concentration of Na+(aq) in a solution that is prepared by mixing 10 mL of a 0.010 M

NaHCO3(aq) solution with 10 mL of a 0.010 M Na2CO3(aq) solution?

A ) 0.010 mole/L

B ) 0.015 mole/L

C ) 0.020 mole/L

D ) 0.030 mole/L

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Post-test Confidence Self-Assessment

Congratulations!

You have completed a test of The Official MCAT® Self-Assessment Package.

Now that you have completed the test, reconsider your confidence rating of your knowledge of the content in

this test. Has your confidence level changed after answering the questions? Why might this be? Both your initial

and revised confidence ranking for each content category will be displayed in the analytic summary.

MCAT®

is a program of the Association of American Medical Colleges

Test/Content Categories

A=1-Not

Confident

at all

B=2-

Somewhat

Confident

C=3-

Moderately

Confident

D=4-Very

Confident

E=5-

Extremely

Confident

1. General Chemistry

Overall

2. Acids and Bases

3. Bonding

4. Electrochemistry

5. Electronic Structure

and Periodic Table

6. Kinetics and

Equilibrium

7. Phases and Phase

Equilibria

8. Solution Chemistry

9. Stoichiometry

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10. Thermodynamics and

Thermochemistry

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Pre-test Confidence Self-

Assessment

1 (A) (B) (C) (D) (E)

2 (A) (B) (C) (D) (E)

3 (A) (B) (C) (D) (E)

4 (A) (B) (C) (D) (E)

5 (A) (B) (C) (D) (E)

6 (A) (B) (C) (D) (E)

7 (A) (B) (C) (D) (E)

8 (A) (B) (C) (D) (E)

9 (A) (B) (C) (D) (E)

10 (A) (B) (C) (D) (E)

General Chemistry Questions

1 (A) (B) (C) (D)

2 (A) (B) (C) (D)

3 (A) (B) (C) (D)

4 (A) (B) (C) (D)

5 (A) (B) (C) (D)

6 (A) (B) (C) (D)

7 (A) (B) (C) (D)

8 (A) (B) (C) (D)

9 (A) (B) (C) (D)

10 (A) (B) (C) (D)

11 (A) (B) (C) (D)

12 (A) (B) (C) (D)

13 (A) (B) (C) (D)

14 (A) (B) (C) (D)

15 (A) (B) (C) (D)

16 (A) (B) (C) (D)

17 (A) (B) (C) (D)

18 (A) (B) (C) (D)

19 (A) (B) (C) (D)

20 (A) (B) (C) (D)

21 (A) (B) (C) (D)

22 (A) (B) (C) (D)

23 (A) (B) (C) (D)

24 (A) (B) (C) (D)

25 (A) (B) (C) (D)

26 (A) (B) (C) (D)

27 (A) (B) (C) (D)

28 (A) (B) (C) (D)

29 (A) (B) (C) (D)

30 (A) (B) (C) (D)

31 (A) (B) (C) (D)

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36 (A) (B) (C) (D)

37 (A) (B) (C) (D)

38 (A) (B) (C) (D)

39 (A) (B) (C) (D)

40 (A) (B) (C) (D)

41 (A) (B) (C) (D)

42 (A) (B) (C) (D)

43 (A) (B) (C) (D)

44 (A) (B) (C) (D)

45 (A) (B) (C) (D)

46 (A) (B) (C) (D)

47 (A) (B) (C) (D)

48 (A) (B) (C) (D)

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50 (A) (B) (C) (D)

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55 (A) (B) (C) (D)

56 (A) (B) (C) (D)

57 (A) (B) (C) (D)

58 (A) (B) (C) (D)

59 (A) (B) (C) (D)

60 (A) (B) (C) (D)

61 (A) (B) (C) (D)

62 (A) (B) (C) (D)

63 (A) (B) (C) (D)

64 (A) (B) (C) (D)

65 (A) (B) (C) (D)

66 (A) (B) (C) (D)

67 (A) (B) (C) (D)

68 (A) (B) (C) (D)

69 (A) (B) (C) (D)

70 (A) (B) (C) (D)

71 (A) (B) (C) (D)

72 (A) (B) (C) (D)

73 (A) (B) (C) (D)

74 (A) (B) (C) (D)

75 (A) (B) (C) (D)

76 (A) (B) (C) (D)

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78 (A) (B) (C) (D)

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80 (A) (B) (C) (D)

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82 (A) (B) (C) (D)

83 (A) (B) (C) (D)

84 (A) (B) (C) (D)

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86 (A) (B) (C) (D)

87 (A) (B) (C) (D)

88 (A) (B) (C) (D)

89 (A) (B) (C) (D)

90 (A) (B) (C) (D)

91 (A) (B) (C) (D)

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93 (A) (B) (C) (D)

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96 (A) (B) (C) (D)

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98 (A) (B) (C) (D)

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101 (A) (B) (C) (D)

101 (A) (B) (C) (D)

102 (A) (B) (C) (D)

103 (A) (B) (C) (D)

104 (A) (B) (C) (D)

Post-test Confidence Self-

Assessment

1 (A) (B) (C) (D) (E)

2 (A) (B) (C) (D) (E)

3 (A) (B) (C) (D) (E)

4 (A) (B) (C) (D) (E)

5 (A) (B) (C) (D) (E)

6 (A) (B) (C) (D) (E)

7 (A) (B) (C) (D) (E)

8 (A) (B) (C) (D) (E)

9 (A) (B) (C) (D) (E)

10 (A) (B) (C) (D) (E)

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