ek_genchem2

Heat Capacity, Phase Change, and Colligative Properties.\.0 ideal bomb calorimeter is an example of a(n):

A. Isolated systemB. Closed systemC. Open systemD. Free system

e heat transfer in a bomb calorimeter corresponds to:

the enthalpy change.the entropy change.the Gibbs free energy change. )the energy change.

·0 solutions at room temperature are mixed in affee cup calorimeter and an exothermic reaction

. As the temperature of the calorimeter rises,transfers:

from the surroundings to the solution.from the solution to the surroundings.

• .·0 heat is transferred between the surroundingsand the solution.

. The direction of heat transfer depends upon roomtemperature.

,- is the heat capacity of a bomb calorimeter and I'lTemperature increase during a reaction, which of

: llowing expression gives the heat transfer?

the combustion of 1 g of benzoic acid,_. produces 26 kJ of energy. In a certain bomb

"'~eter. a 10°C temperature increase is observed:: g of benzoic acid are combusted. What is the

_'...G.O.JO<U..ityof the calorimeter?

, ustion of hydrazine, N2H4, produces nitrogen- . 'ater vapor. The heat of combustion for this

. - . -618 kl/mol. If 1.6 g or hydrazine arezsted in a bomb calorimeter at 298 K and with a

~ <:::!?aci"£}' of 6.2 kJtC, what will be the temperatureb calorimeter after the reaction?

Phase Changes

620. When water melts, what kind(s) of bonds are breaking?

I. CovalentII. Ionic

III. Hydrogen

A. I onlyB. III onlyC. I and II onlyD. I and III only

621. When sodium chloride melts, what kind(s) of bonds arebreaking?

I. CovalentII. Ionic

III. Dipole-dipole

A. I onlyB. II onlyC. III onlyD. II and III

622. Put the following compounds in order of boiling pointfrom highest to lowest?

I. H2OII. NH3

III. CH4

A. I, II, IIIB. I, III, IIC. II, III, ID. III, II, I

623. When dry Ice (C02) melts, what kind of bonds arebroken?

A. IonicB. CovalentC. IntermolecularD. Metallic

624. When sodium hydrogen phosphate (Na2HP04) melts,what kind of bonds are broken?


625. When diamond melts, what kind of bonds are broken?


67Copyright © 2005 ExamKrackers, Inc.

1001 Questions in MCAT Chemistry626. When copper melts, what kind of bonds are broken?


627. Which of the following compounds should have thehighest boiling point?

A. BrCIB. Br2C. ICID. Xe

628. When mass spectrometry is performed on a sample ofhydrogen fluoride gas, a large peak is seen at 20 amu,with successively smaller peaks at 40 amu, 60 amu, 80amu, and 100 amu. When hydrogen chloride is usedinstead, only one peak at 36.5 amu is seen. What is anexplanation for this?

A. The hydrogen fluoride dissociates at high energiesB. Hydrogen bonding allows the HF molecules to

form small associations in the vapor phaseC. Hydrogen chloride is ionic while hydrogen fluoride

is covalentD. Hydrogen chloride is a liquid under standard

conditions, while hydrogen fluoride is a gas

629. If a solid at a temperature below its melting point isheated, the added energy:

I. breaks bonds.II. increases the translational kinetic energy of the

molecules.III. increases the vibrational kinetic energy of the

molecules.

A. I onlyB. II onlyC. III onlyD. I, II, and III

630. If a solid at its melting point is heated, the addedenergy:

I. breaks bonds.II. increases the translational kinetic energy of the

molecules.III. increases the vibrational kinetic energy of the

molecules.

A. I onlyB. II onlyC. III onlyD. I and II only

631. If a liquid at a temperature below its boilingheated, the added energy:

I. breaks bonds.I!: increases the translational kinetic energy

molecules.III. increases the vibrational kinetic energy

molecules.

z:

A. I onlyB. III onlyC. I and II onlyD. II and III only

632. If a liquid at its boiling point is heated, theenergy:

I. breaks bonds.II. increases the translational kinetic energj

molecules.III. increases the vibrational kinetic energy

molecules.

A. I onlyB. II onlyC. III onlyD. I and II only

633. Which of the following gives an approximatethe heat of sublimation of a substance?

A. Add the heat of vaporization and the hB. Subtract the heat of fusion from

vaporizationC. Multiply the heat of formation by

vaporizationD. Divide the heat of reaction by the heat of .:IL AN-

634. Which of the following physical processoccurring in a pure substance is accomparaecincrease in temperature?

I. meltingII. vaporization

III. sublimation

A. I onlyB. I and II onlyC. I, II, and IIID. None are accompanied by a temperature r,:='"'Z'P

635. 3 grams of solid H20 are heated to O°c. If. _this temperature is reached, 6 more caloriesthe temperature of the H20 will be:

A. O°CB. 2°CC. 3°CD. 6°C


Heat Capacity, Phase Change, and Colligative Properties-'-heat of fusion of 80 cal/g and a heat of Questions 641-647 utilize this heating curve for 10 grams of

•• m:=::::.:::; of 540 cal/g. How much heat is required to an unknown substance:grams of ice at O°C to steam at 100°C?

cal- 540) cal

1000) cal- 100 + 540) cal

- a heat of fusion of 80 cal/g and a heat of"1Ir.z:t:::::.J!::. of 540 call g. If it takes 10 minutes to heat

- arer from 20°C to 100°C, and the heat is*1:'2::-::.:'- - a constant rate, how much longer does it

e water to be converted to steam?

1 minute~...."..,'"'"""1 minute and ten minutes

een ten minutes and one hourone hour

le of water is evaporating at a temperatureboiling point, what happens to the

"C:I::re:::::::=e of the liquid phase?

-- to cool, since the most rapidly moving-L.=_~lesare leaving the liquid phase

-- to cool, since the transition from liquid to·- exothermic

~- to heat, since the transition from liquid to·- exothermic•- to heat, since the gas phase has a higher.;-than the liquid phase

containing an unknown liquid is placed in a~ n bath. The temperature drops rapidly to

rises to -32°C. It remains at -32°C for~ and then drops again, rapidly at first, and_ slowly. Finally, the temperature stabilizes at

=c.. 'hich of the following can be concluded from')

zing point of the liquid is -32°C- freezing point of the liquid is -35°C

--= freezing point of the liquid is -196°Czing point of the nitrogen is -32°C

be preserved by removing water via,...._~·on in a process called freeze-drying. Freeze

: r bably occurs at:

- emperatures and pressures.- temperatures and high pressures.

_ temperatures and low pressures.._ temperatures and pressures.

1200

/ I1000 iI800 ~

~ /~<II 60, Conducting solid I

/•... V", i::J- \ / !IV 400•... \ V ~u)D !<IIQ.

E 200\ / i

<IIt-

o /'-200 ('------f Insulating solid I I i

-400 I I Ia 1000 2000 3000 4000 5000 6000

Heat (cal)

641. Which phase of this substance has the greatest specificheat?

A. Insulating solidB. Conducting solidC. LiquidD. Vapor

642. What is the melting point of this substance?

A. -170°CB. 350°CC. 2400°CD. Cannot be determined from this graph

643. If the pressure exerted on the liquid is increased, themelting point:

A. will increase.B. will decrease.C. will remain the same.D. cannot be determined from the information given.

644. If the pressure of the gas above the fluid is increased,the boiling point of the substance will:

A. IncreaseB. DecreaseC. Remain the sameD. Cannot be determined from the information given

645. What is the latent heat of fusion of this substance?

A. 20 cal/gB. 240 cal/gC. 260 cal/gD. Cannot be determined from this graph


1001 Questions in MCAT Chemistry646. What is the specific heat of the vapor phase of this

substance?

A. 0.08 cal/g=CB. 0.2 cal/gOCC. 0.5 cal/gOCD. 1.0 cal/g=C

647. Starting at -200°C, how much heat would have to beremoved from the substance to bring it to -400°C?

A. 50 caloriesB. 100 caloriesC. 200 caloriesD. It is impossible to bring the substance to -400°C

648. Ice is just beginning to form on a winter lake. Where isthe lake the coldest?

A. At the top of the lakeB. At the bottom ofthe lakeC. At the middle depths of the lakeD. The lake is the same temperature everywhere.

Use the diagram and formula below to answer questions649-651. The diagram below shows the In(Pvapor)vs. liT forfour substances. The Clausius-Clapeyron equationdescribes this relationship.

~&l:::

xw

zlIT(K)

I (P ) - - I1Hvap(l)n vap- R T+C

The Clausius-Clapeyron Equation

649. According to the graph, at high temperatures, whichsubstance has the greatest vapor pressure?

A. WB. XC. YD. Z

650. Which substance has the greatest heat ofvaporizati

A. WB. XC. YD. Z

651. If X is water, which line could represent diethyl et

(C2Hs)20?

A. WB. XC. YD. Z

Phase Diagrams

Use the phase diagram below to answer questions 652-66~

y

A-

B-~~:r-rlf:::::::j::~:::t::::::::uQ :S

RT

652. From the diagram, which of the following repressolid, liquid, and gas respectively?

A. X,Y,ZB. Y,X,ZC. Z,X, YD. X,Z,Y

653. If the phase diagram is of water, whichrepresent one atmosphere of pressure?

A. AB. BC. CD. D

654. If the phase diagram is of water, which line coulrepresent 100°C?

A. RB. SC. TD. U


Heat Capacity, Phase Change, and Colligative Properties655. If the phase diagram is of water, and line A is one atm, 662. If a small amount of salt were added to the substance

which line could represent 0 DC? forming a solution, which of the following couldrepresent the phase diagram of the solution? (The darklines represent the equilibrium lines of the puresubstance and the dashed lines represent theequilibrium lines of the solution.)

A. QB. Re. SD. T

656. If the phase diagram is of water, and line A is one atm,can ice, liquid water, and water vapor exist inequilibrium at 0 °C and 1 atm?

A. No, because the triple point is below 1 atm.B. No, because the triple point is below 0 DC.e. Yes, because ice and water can have an

equilibrium with the vapor phase regardless of thepressure or temperature.

D. Yes, because 1 atm and 0 °C is above the triplepoint.

657. Why might this phase diagram resemble water?

A. There are three phases represented.B. The equilibrium line between solid and liquid

slopes up and to the left.e. The equilibrium line between liquid and gas slopes

up and to the right.D. The equilibrium line between solid and gas slopes

down and to the left.

658. Which line goes through the triple point?

A. QB. RC. SD. U

659. At constant pressure C, what does the substance do astemperature increases at Q?

A. condenseB. sublimee. depositD. melt

660. If the substance is held at a constant temperature S, andpressure is increased from very low to very high, thesubstance:

A. condensesB. depositsC. evaporatesD. freezes

661. Which of the following represents the criticaltemperature?

A. QB. Re. SD. U

A. e.

B. D.

663. A substance at a temperature and pressure above itscritical temperature and pressure is called:

A. plasmaB. gasC. supercritical fluidD. hyperphased

664. Which of the following is NOT true for supercriticalfluid?

A. It will not become a liquid no matter how great thepressure.

B. It will not become a liquid no matter how low thetemperature.

e. The liquid and vapor phases are indistinguishable.D. It is found at temperatures and pressures above the

critical temperature and critical pressure.

665. A substance is dissolved in supercritical CO2, If thesolution is allowed to equilibrate at room temperatureand pressure, the CO2 will:

A. boil out of solution.B. precipitate out of solution.e. condense and remain in solution.D. condense and separate out of solution.

71I Copyright © 2005 ExamKrackers, Inc.

1001 Questions in MCA T Chemistry666. On a diagram of pressure versus temperature, how does

the transition between liquid and gas phases appear?

A. As a pointB. As a straight line segmentC. As a quadrilateral regionD. As a curved line segment

667. At which of the following combinations of temperatureand pressure can the solid, liquid, and vapor phases of asubstance coexist in equilibrium?

A. STPB. standard conditionsC. critical pointD. triple point

668. Is it ever possible for liquid water to be transformedinto water vapor without undergoing a sharp phasetransition?

A. Yes, if an experimenter raises the pressure andtemperature of the water until the critical point ispassed, then lowers the pressure, and then lowersthe pressure and temperature until the vapor phaseis reached.

B. Yes, if an experimenter lowers the temperature ofthe water until it freezes, and then allows it toundergo sublimation to the vapor phase.

C. No, it is never possible to change from liquid tovapor without a sharp phase transition.

D. No, it is possible for amorphous substances tochange from liquid to vapor without a sharp phasetransition, but water is not an amorphoussubstance.

Use the following information and the diagram, belowanswer questions 669-676. Water and butanol are partiamiscible. At room temperature, when equal amountswater and butanol are poured into the same container, twphases are formed, one containing mostly water with a SIlt

amount of butanol, and one containing mostly butanol withsmall amount of water. At some critical solution temperawater and butanol are completely miscible and only 0

phase exists for any mixture. The miscibility graph beloshows temperature vs. mole fraction for a hypothetical FluiX with water at a constant pressure of I atm. The shadregion represents the two phase system and the light regiorepresents the one phase system.

TOne phase

A

TJ

_L [3

.I/

E

0------ x ------------~~ 1

669. Which point on the diagram is at the critical solutiontemperature?

A. AB. BC. DD. E

670. What does the system look like at point C!

A. A small amount of Fluid X dissolved in waterB. A small amount of water dissolved in Fluid XC. A homogeneous mixture of equal amounts of Fluid

X and water.D. A two phase system of water and Fluid X with

more Fluid X than water.

72Copyright © 2005ExamKrackers, Inc.

674. Water and triethylamine are only partially miscible athigh temperatures, but become completely miscible atlow temperatures. Which of the following mightrepresent the miscibility graph for water andtriethylamine?

671. What does the system look like at point D?Heat Capacity, Phase Change, and Colligative Properties


A. A heterogeneous mixture of a small amount ofFluid X dissolved in water in one phase and a smallamount of water dissolved in Fluid X in the otherphase.

B. A two phase system with both phases containing anequal amount of water and Fluid X.

C. A homogeneous mixture of equal amounts of FluidX and water.

D. A two phase system of water and Fluid X withmore Fluid X than water.

672. A student pours 100 mL of pure water into a 500 mLbeaker. The student adds 10 mL of Fluid X stirs andallows the mixture to come to equilibrium. The studentrepeats this process until the beaker is full. If the entireexperiment is performed at temperature T), which of thefollowing describes the system during this experiment?

A. Initially Fluid X dissolves completely in water toform a single phase. When enough Fluid X isadded, a second phase of water dissolved in FluidX begins to form. As the amount of Fluid Xincreases, the water from the first phase isdissolved into the Fluid X to form a single phase.

B. A two phase system with Fluid X in one phase andwater in the other phase remain separatethroughout the experiment.

C. Initially Fluid X dissolves completely in water toform a single phase. As more Fluid X is added, theFluid X begins to predominate so that water isdissolved in Fluid X. One phase is maintainedthroughout.

D. Initially Fluid X dissolves completely in water toform a single phase. As the solution nears thecritical solution temperature, equal amounts ofFluid X and water form two separate phases. Asthe amount of Fluid X increases still further, thewater from the first phase is dissolved into theFluid X to form a single phase.

673. Fluid X 'is probably:

A. nonpolar.B. polar, but less polar than water.C. exactly as polar as water.D. more polar than water.

A. C.

TT

Ol---X-- .•·l O---X--··l

B. D.TTII-__ ---""'f

675. Below is the miscibility graph for water and butanol.What is the critical solution temperature for water andbutanol?

150

2

0 X • 1

A. 25°CB. 50°CC. 125°CD. 150°C

1001 Questions in MCAT Chemistry


Use the diagram below to answer questions 676-681. Belowis a phase diagram for elemental sulfur.

104

.Liquid

102

II o

~ 10-2

:5uRhombic 0~

0:;sI I

10-4

10-6 Gas

40 80 120 160

tin °C

676. According to the phase diagram above, which of thefollowing phases of sulfur can exist at 1 atm?

I. RhombicII. Monoclinic

III. Liquid

A. I onlyB. II onlyC. III onlyD. I, II, and III

677. According to the phase diagram above, how many triplepoints does sulfur have?

A. zeroB. oneC. twoD. three

678. Which of the following phases of elemental sulfurmostly likely has a zero standard enthalpy of formationat room temperature?

A. RhombicB. MonoclinicC. LiquidD. Gas

679. A sample of sulfur is initially at 1 atm and 60°C. Thepressure on the sample is decreased to 10-6 atm. Nextthe temperature is increased slowly to 90 "C.According to the phase diagram, which of the followingare the phase changes experienced by the sample?

A. sublimationB. vaporizationC. transition and vaporizationD. transition and condensation

680. A sample of sulfur is initially at 10-6 atm and 70°C. If.the pressure on the sample is increased, what phasechange will the sample experience?

A. sublimationB. depositionC. vaporizationD. fusion

681. The Frosch process is used to mine sulfur. In theFrosch process water is pumped into a sulfur deposit at1 atrn to melt the sulfur. Compressed air then forcesthe sulfur to the surface where it is cooled andcollected. Which of the following must true in orderfor this process to occur?

A. The sulfur deposit must exist as monoclinic sulfur.B. The water used to melt the sulfur must be

superheated.C. The compressed air must be at a pressure. less than

one atmosphere.D. The sulfur is ultimately collected as a gas.

Use the diagram below to answer questions 682-689. Theisotherms of H20 are shown as solid lines on pressure vs.molar volume phase diagram below.

Platm

218

85

400°C

\' 374°C\ vapor

'i ' - 300°Cliquid + vapor ~ 200°C

15

v

682. What are the critical pressure and temperature of water?

A. 15 atrn and 200°CB. 85 atrn and 300°CC. 218 atrn and 374°CD. above 218 atm and 400°C

683. Which of the following describes the volume changethat occurs along the horizontal section of the 200 °Cisotherm moving from left to right?

A. The volume decreases as the pressure goes up.B. The volume is decreases as water condenses.C. The volume increases as the pressure goes down.D. The volume increases as water is vaporized.

Heat Capacity, Phase Change, and Colligative Properties684. What is the boiling point of water at 85 atm?

A. 200 DCB. 300 DCC. 374°CD. 400DC

685. What is the minimum pressure required to convert H20to liquid water at 400 DC?

A. less than 218 atmB. 218 atmC. Greater than 218 atmD. H20 will not turn to liquid at 400 DCno matter how

great the pressure.

686. At which of the following temperatures is liquid H20impossible?

A. 200 DCB. 374 DCC. 400 DCD. H20 liquid can exist at any temperature if the

pressure is high enough.

687. What is the name for H20 at 219 atm and 375°C?

A. liquidB. vaporC. supercritical fluidD. ice IX

688. As we follow the 200 DC isotherm from left to right,which of the following describes the energy flow?(Assume ideal behavior for water vapor.)

A. The net energy flow is zero along the entire path.B. The net energy flow is into the sample along the

entire path.C. The net energy flow is out of the sample along the

entire path.D. The net energy flow is into the sample along the

horizontal portion of the path, and zero at all otherpoints.

689. As we follow the 200 DC isotherm from left to rightbefore it enters the liquid and vapor area, which of thefollowing describes the energy flow?

A. Work is done on the sample and heat is releasedfrom the sample.

B. Work is done on the sample and heat is absorbedby the sample.

C. Work is done by the sample and heat is releasedfrom the sample.

D. Work is done by the sample and heat is absorbedby the sample.

Colligative Properties

690. Colligative properties depend upon:

A. quality not quantity.B. size not charge.C. number not kind.D. mass not size.

691. Which of the following is NOT a colligative property?

A. Boiling point elevationB. Osmotic pressureC. Vapor pressure loweringD. Heat of solution

692. Which of the following is true when a nonvolatilesolute is added to a pure liquid?

A. The melting and boiling points decrease.B. The melting and boiling points increase.C. The melting point increases and the boiling point

decreases.D. The melting point decreases and the boiling point

increases.

693. Why does the boiling point rise when a nonvolatilesolute is added to a pure liquid?

A. Because the density of the solution becomesgreater than the density of the pure liquid.

B. Because the kinetic energy of the molecules of theliquid in the solution is less than the kinetic energyof the molecules in the pure liquid.

C. Because adding a solute to a liquid cools the liquid.D. Because solute molecules occupy surface area of

the liquid and lower the vapor pressure.

694. Why does the freezing point drop when a nonvolatilesolute is added to a pure liquid?

A. Because the solute disrupts the formation of asymmetrical crystalline structure.

B. Because the kinetic energy of the molecules of theliquid in the solution is less than the kinetic energyof the molecules in the pure liquid.

C. Because adding a solute to a liquid warms theliquid.

D. Because solute molecules occupy surface area ofthe liquid and lower the vapor pressure.


1001 Questions in MCAT Chemistry


695. Fanners who have to leave fruit in unheated storagerooms sometimes put the fruit next to large containersof water to keep the fruit from freezing. Why wouldthis method work?

A. The water moistens the fruit, and the higher watercontent of the fruit decreases its freezingtemperature, protecting the fruit.

B. The water absorbs humidity from the environment,drying out the fruit, and the fruit can then becomecold without danger of ice crystals forming.

C. Because the water in fruit contains dissolved sugar,the fruit freezes at a higher temperature than thewater, so although the fruit does freeze, it is lessseriously damaged.

D. Because the water in fruit contains dissolved sugar,the container of water freezes at a highertemperature than the fruit. The freezing waterreleases heat, which prevents the temperature in theroom from dropping until all the water is frozen.

696. Which of the following aqueous solutions would havethe lowest freezing point?

A. 0.10 MCaClzB. 0.45 MNaN03

C. 0.65MHClD. 0:90MNH3

697. The freezing-point depression constant of water is 1.86KIm. What concentration of sodium chloride isnecessary to cause a container of water to freeze at-5°C?

A. 1.3 mB. 1.86 mC. 3.0 mD. 5.0m

698. Cyclohexane has a freezing point of 6.5°C and afreezing-point depression constant of 20.1 KIm. If a0.01 m solution of acetic acid is dissolved in thecyclohexane, what is the freezing point of the mixture?(Acetic acid does not dissociate in cyclohexane.)

A. O°CB. 0.2°CC. 4.8°CD. 6.3°C

699. Acetone has a boiling point of 56.2°C and a boiling-point elevation constant of 1.71 KIm. If 2.0 grams ofdimethyl ether (C2H60) are dissolved in 100 grams ofacetone, what is the boiling point of the resultingsolution? (Assume that dimethyl ether does notdissociate in acetone.)

A. 56.2°CB. 56.9°CC. 59.6°CD. 90.2°C

700. 20 grams of an unknown non-volatile substance isdissolved in 1.0 kg of a solvent, and the resultingfreezing point of the solvent is measured and comparedto the freezing point of the pure solvent. In order tocalculate the molecular weight of the unknown solvent,what else must be known?

I. The freezing-point depression constant of thesolvent

II. The degree to which the solute ionizes in thesolvent , c

III. The density of the resulting solution

A. I onlyB. II onlyC. I and II onlyD. I, II, and III

701. When 10 grams of a certain alkane is dissolved in 1 kgof benzene, the freezing point is found to be 4.9°C.Which of the following is most likely to be the alkane?(Benzene has a freezing point of 5.5°C and a freezing-point depression constant of 5.1 KIm.)

A. Ethane (C2H6)B. Butane (C4HIO)

c. Hexane (C6H14)

D. Octane (C8H18)

702. When 10 grams of a certain material are dissolved in 1kg of water, the freezing point of the solution is-0.46°C. Which of the following could be thesubstance? (Water has a freezing-point depressionconstant of 1.86 KIm.)

A. HC2H302B. HN03

C. NaClD. CaCh

Heat Capacity, Phase Change, and Colligative Properties03. According to the equation !1T = Kmi, the freezing point 707. If a solution with high osmotic pressure is separated

of 0.1 MNaCI solution should be -0.372 0C. However, from a solution with low osmotic pressure by athe experiment gives a value of -0.348 °C. Which of membrane permeable only to water:the following might explain this discrepancy?

A. Precipitation results in fewer particles in solution.B. Ion pairing between Na+ and cr ions results in

fewer particles in solution.c. Under real conditions impurities in the water create

more particles.D. Water auto ionizes creating more particles in'

solution.

704. The van't Hoff factor found by experiment is often lessthan the theoretical van't Hoff factor. If !1Tc is thechange in temperature calculated assuming nodissociation and !1To is the change in temperature foundby experiment, which of the following might give thevan't Hoff factor found by experiment?

A. !1Tc!1ToB. l/(I'lTc!1To)C; !1Tcf!1ToD. I'lTJ!1Tc

705. The observed van't Hoff factor is often found to be lessthan the theoretical van't Hoff factor. Is thisdiscrepancy increased or decreased when the solution isdiluted?

A. Decreased, because there is more ion pairingB. Decreased, because there is less ion pairing.C. Increased, because there is more ion pairing.D. Increased, because there is less ion pairing.

706. A container filled with water is divided in half by asemipermeable membrane. When salt is placed in onehalf of the container.ithe water level on one side of thecontainer rises above the level on the other side. Whichof the following is an accurate description of thisprocess?

A. Since evaporation occurs more readily in the sidewith the salt, that side will have the lower waterlevel.

B. Since the concentration of water is higher on thepure water side, more water will flow to that side,and the water level of the salt side will be lower.

C. Since the concentration of water is higher on thepure water side, more water will flow from thatside to the other side, and the water level of the saltside will be higher.

D. It is impossible for an unequal distribution of waterto occur; if water can flow from one side toanother, the levels will always equalize.

A. water will tend to move into the solution with highosmotic pressure.

B. water will tend to move into the solution with lowosmotic pressure.

C. solute will tend to move into the solution with highosmotic pressure.

D. solute will tend to move into the solution with lowosmotic pressure.

708. A swimming pool is filled with pure water and thehydrostatic pressure at a certain depth is measured at2.5x104 Pa. Salt is added to the water in the pool.After the salt dissolves, the pressure will be equal to:

A. the hydrostatic pressure plus the osmotic pressure.B. the hydrostatic pressure plus the osmotic pressure.C. the hydrostatic pressure only.D. the osmotic pressure only.

709. 0.0 I mole of glucose is added to one liter of water at 25°C and 1 atm. The osmotic pressure is 0.24 atm. Whatis the total pressure in the container?

A. 0.24 atmB. 0.76 atmC. 1 atmD. 1.24 atm

710. When placed in a hypertonic solution, a red blood cellundergoes crenation (it shrivels). The cell undergoescrenation because:

A. the osmotic pressure inside the cell is less than theosmotic pressure outside the cell.'

B. the osmotic pressure inside the cell is greater thanthe osmotic pressure outside the cell.

C. the hydrostatic pressure inside the cell is less thanthe hydrostatic pressure outside the cell.

D. the hydrostatic pressure inside the cell is greaterthan the hydrostatic pressure outside the cell.


~-

1001 Questions in MeAT Chemistry


711. A U-shaped tube with a semi-permeable membrane atits lowest point is filled with water, as shown below.(The water heights as indicated in the diagram representinitial conditions.) If the left half of the tube containsglucose at a concentration of 3 molar, which of thefollowing expressions could be used to estimate thedistance, in meters, that the water on the left side rises?(The ideal gas law constant is 8.314 Jzmol K. Assumethat the temperature is 2rC.)

3MGlucose

PureWater

A. (8.3)(27)

@)(1000)(9.8)B. @)(8.3)(27)

(1000)(9.8)C. @)(8.3)(300)

(1000)(9.8)

D. (8.3)(300)@)(1000)(9.8)

712. Suppose a membrane were found which was permeableto ions but not to isobutanol. If this membrane wereused to separate a solution of NaCI in isobutanol frompure isobutanol, which side would reach the higherlevel?

A. The salt side, due to osmotic pressureB. The pure isobutanol side, since the salt will flow

out but not inC. Neither side, since the solvent cannot pass through

the membrane.D. It would depend on whether the volume of the pure

solvent increased or decreased when salt wasadded to it.

Use the following information to answer questions 7l3-715.Orderly systems possess more free energy than disorderlysystems. In solutions solute molecules disrupt the naturalorder of a pure liquid. Osmotic potential is the free energy ofa solution under constant temperature and pressure. Purewater is arbitrarily assigned an osmotic potential value ofzero. Water spontaneously flows from high to low osmoticpotential.

713. Based on the information above, the osmotic potentialof an aqueous solution ofNaCl:

A. is negativeB. is positiveC. is zeroD. may be either negative or positive.

714. The decrease in the osmotic potential of watermolecules is directly proportional to the osmoticconcentration. Which of the following solutions hasthe lowest osmotic potential?

A. 0.9 MNaCIB. 0.9 M glucoseC. 1 MNaCID. 1 M glucose

715. Unlike osmotic potential, water potential is a functionof temperature and pressure as well as soluteconcentration. When two solutions are separated by amembrane permeable to water but not solute, water willmove from higher water potential to lower waterpotential. As the hydrostatic pressure of a solutionincreases, the water potential:

A. decreases because the water molecules have lessspace and so become more ordered.

B. remains constant because water has no place tomove.

C. remains constant, because temperature increases.D. increases because the water molecules have more

free energy.

Definitions

716. The definition of pH is:

A. 10g[H+]B. -log[W]C. 7D. the number of hydrogen ions in solution.

717. Which of the following defines a neutral solution?

A. pH=7B. [H+] = [OH-]C. [W] =0D. A solution where acids don't donate protons and

bases don't accept protons.

718. The autoionization of water (shown below) IS anendothermic reaction.

2H20 ~ H30+ + OW

as the temperature of pure water increases the pH:

A. decreases because [H+] increases.B. increases because [OH-] increases.C. increases because [H+] increases.D. remains at 7 because [H+] equals [OH-] even after

an equilibrium shift.

719. Which of the following is true of the equilibrium for theautoionization of water (shown below)?

2H20 ~ H)O I + OIr

A. The equilibrium lies a little to the left.B. The equilibrium lies far to the left.C. The equilibrium lies far to the right.D. The equilibrium is balanced evenly between the

left and the right.

720. All of the following are true concerning acids and basesEXCEPT:

A. acids taste sour.B. bases taste bitter.C. bases are slippery.D. acids are sticky.

721. Which of the following is NOT a way of defining anArrhenius acid?

A. An Arrhenius acid is a substance that increases theH+ concentration in aqueous solution

B. An Arrhenius acid is a substance that increases thepH of an aqueous solution

C. An Arrhenius acid is a substance that increases thepOH of an aqueous solution

D. An Arrhenius acid is a substance that decreases theOH- concentration in an aqueous solution

Acids and Bases

I. HClII. CH CH_OH

III. BF3

A. I onlyB. monlyc. I and II onlyD. I, II, and m

723. Which of the following can act as Bronsted-Lowryacids in some circumstances?

I. HCIII. CH3CH20H

III. BF)

A. IonlyB. III onlyC. I and II onlyD. I, II, and III

724. Which of the following can act as Lewis acids in somecircumstances?

I. HCIII. CH3CH2OH

III. BF)

A. I onlyB. III onlyC. I and II onlyD. I, II, and III

725. In the following reaction, which substance is acting as aBronsted-Lowry acid?

NH3+H- ~ NH2-+H2

A. NH3B. WC. NH4+D. NH2-

726. Which of the following is NOT possible?

A. A Lewis acid that is not a Bronsted-Lowry acidB. A Bronsted-Lowry acid that is not a Lewis acidC. A substance that is sometimes a Lewis acid and

sometimes a Lewis baseD. A substance that is sometimes a Bronsted-Lowry

acid and sometimes a Bronsted-Lowry base


1001 Questions in MeAT Chemistry


727. A warning sign in an industrial laboratory says "Do notstore acids with bases! Acids go in cabinet A, bases incabinet B." The definition of acid and base that thissign is using is most likely:

A. the Arrhenius defmition, since unlike the Bronsted-Lowry and Lewis definitions, it is not possible fora substance to be sometimes an acid and sometimesa base.

B. the Bronsted-Lowry definition, since it is thedefinition most commonly used.

C. the Lewis definition, since it involves reactionsbetween substances.

D. the Lewis definition, since it can be applied toalmost all substances.

728. BF3 is a very effective Lewis acid. Which of thefollowing is a reasonable explanation for thisobservation?

A. BF3 contains fluorineB. BF3 is negatively chargedC. BF3 has an empty orbital in its valence shellD. BF3 holds its protons very loosely

729. What is the pH of a solution with a hydrogen IOnconcentration of 1.0x10-4 M?

A. -4B. -0.0001C. 0.0001D. 4

730. What is the pH of a solution with a hydrogen ionconcentration of3.0x10-4 M?

A. 3.0B. 3.5C. 4.0D. 4.5

731. What is the hydrogen ion concentration in a solutionwith pH 11.26?

A. 5.5xlO-12

B. 5.5x10-11

C. 5.5xlO-IO

D. 1.12x10-6

732. 1 mL of a strong acid solution has a pH of 2.3. It isdiluted with water to make a 100-mL solution. What isthe new pH?

A. 0.023B. 2.3C. 4.3D. 230

733. What is the conjugate base of ammonia?

A. NH2-

B. NH3C. NH/D. OW

734. What is the conjugate base of HC03-?

A. H2C03B. C03

2-

C. H20D. OW

735. What is the conjugate base ofH30+?

A. H20B. HPC. OH-D. H202

736 .. What is the conjugate acid of phosphoric acid?

A. H2P04-

B. H3P04

C. H4PO/D. H30+

737. Which of the following conducts electricity the mostpoorly?

A. NaCI(I)B. NaCl(aq)C. HCI(aq)D. HClO(aq)

738. Which of the following is the weakest acid?

A. Hydrochloric acidB. Sulfuric acidC. Nitric acidD. Formic acid

739. Which of the following is amphiprotic m aqueoussolution?

I. HClII. HPO/-

III. H2O

A. I onlyB. II onlyC. I and II onlyD. II and III only

Acids and Bases· Which of the following is NOT true concerning

conjugate bases?

A. Every acid has a conjugate base.B. The conjugate base of a Bronsted-Lowry acid IS

that acid minus its acidic proton.C. Some conjugate bases are acidic.D. OH- is the conjugate base ofH30+.

· Which of the following is most useful for calculatingthe pH of a solution?

A. The strength of the conjugate baseB. TheKa

C. The concentration of hydrogen ionsD. The concentration of the acid

· Which of the following is NOT true?

A. Strong acids have weak conjugate bases.B. Weak acids have strong conjugate bases.C. The weaker the acid, the stronger its conjugate

base.D. The stronger the acid, the weaker its conjugate

base.

IfHA is a stronger acid than H30+;

A. HA will transfer its proton to H20 more effectivelythan H30+ will transfer its proton to A-.

B. H30+ will transfer its proton to H20 moreeffectively than HA will transfer its proton to A-.

C. HA will transfer its proton to A-more effectivelythan H30+ will transfer its proton to H20.

D. HA will transfer its proton to H30+ moreeffectively than H20 will transfer its proton to A-.

Which ofthe following is the weakest acid?

A. HCI04B. H30+C. RBrD. HN03

'hich of the following is the strongest acid?

HFHCIRBrHI

'hich of the following is the weakest base?

IrNa20N3-

OIr

747. Which of the following is the weakest base in aqueoussolution?

A. KOHB. Ca(OH)2C. Mg(OH)2D. OH-

748. Place the following in order from strongest to weakestbase?

I. ClO-II. H2O

III. crA. I, II, IIIB. I, III, IIC. II, I, IIID. III, I, II

749. Which of the following factors determine the percentionization of an acid?

I. temperature of solutionII. identity of acid

III. concentration of acid

A. II onlyB. I and II onlyC. II and III onlyD. I, II, and III

750. Which of the following IS true concernmg percentdissociation of an acid?

A. Percent dissociation increases with concentration.B. Percent dissociation is 100% for strong acids

regardless of concentration.C. Percent dissociation typically decreases as

temperature increases.D. Percent dissociation is greater for stronger acids.

751. In biological systems, many reactions involve protontransfers. What is one ramification of this observation?

A. Most biological reactions occur under low pHconditions.

B. Most biological reactions occur under high pHconditions.

C. In living organisms, small fluctuations in pH cancreate large rate changes.

D. In living organisms, large fluctuations in pH arerequired to create small rate changes.

752. Which of the following expressions gives the pH of abuffered solution?

A. 10g[H+]B. -log[H+]C. pKa - log([ A-]/[HA DD. pKb + 10g([A-]/[HAD


1001 Questions in MCAT Chemistry759. Rank the following oxyacids from strongest acid to

weakest acid in aqueous solution?


753. If the pH is increased by one pH point, the protonconcentration is:

A. decreased by a factor of two.B. decreased by a factor of ten.e. increased by a factor of two.D. increased by a factor of ten.

754. Compared to a solution with a pH of 5, how many H+ions are in a solution with a pH of3?

A. 4 times as manyB. 10 times as manyC. 20 times as manyD. 100 times as many

755. Alcohols are weaker acids than water. Pure water has apH of 7. A pH greater than 7 indicates a base. Howcan alcohols be weaker acids than water without beingbases?

A. Alcohols are slightly basic.B. A pH lower than 7 doesn't always indicate a base.C. Alcohols are less willing to give up their acidic

hydrogen to a base than is water.D. Water is slightly acidic.

Factors Determining Acid Strength

756. In a series of oxyacids, the acidity increases:

A. as the number of hydrogens attached to the centralatom decreases.

B. as the number of hydrogens attached to the centralatom increases.e. as the oxidation number of the central atomdecreases.

D. as the oxidation number of the central atomIncreases.

757. Which of the following oxides forms a base whendissolved in water?

A. KzOB. COzC. SOzD. NOz

758. Which of the following oxyacids is the strongest acid inaqueous solution?

A. HCIOB. HCI02

C. HCI03

D. HCl04

I. HCIOII. HBrO

III. RIO

A. I, II, IIIB. II, III, Ie. III, II, ID. III, I, II

760. Why are oxyacids with more oxygens around thecentral atom stronger acids?

A. Because each oxygen can take on a protonB. Because oxygens are electron withdrawing and can

neutralize hydroxide ions.C. Because oxygens around the central atom

strengthen the bond between the oxygen and theacidic hydrogen.

D.. Because oxygens around the central atom withdrawelectrons increasing the polarity of the bondbetween the oxygen and the acidic hydrogen.

761. H represents the acidic proton on conjugate base X-.Which of the following tends to decrease the acidity ofHX:

A. a polar H- X bond.B. a strong H-X bond.e. a stable conjugate base X-.D. a high temperature.

Hydrides

762. What is a hydride?

A. A metal atom without a hydration shellB. Compounds that have been formed by the removal

of water.e. Compounds containing only two elements where

one of the elements is hydrogenD. Compounds containing hydrogen.

763. Which of the following molecular hydrides has thehighest boiling point?

A. SiH4B. HzTeC. HzSD. SnH4

Acids and Bases- . On the periodic table, the acidity of hydrides increases

moving from: Equilibrium Constants for Acid-Base Reactions

n..,L-UUYl1~UL \81 ~UQ.J C"\.,,,"I<. """"h~f oJ, l:, •....

I. left to right.II. right to left.

III. top to bottom.

A. I onlyB. II onlyC. I and III onlyD. II and III only

-65. Which of the following is generally true concerninghydrides (other than NH3)?

A. All hydrides are acidic or neutral,B. All hydrides are basic or neutral.C. Metal hydrides are acidic or neutral, while

nonmetal hydrides are basic or neutral,D. Metal hydrides are basic or neutral, while nonmetal

hydrides are acidic or neutral.

-66. Which of the following is the strongest acid?

A. H20B. H2SC. H2SeD. H2Te

-67. Which of the following is NOT a strong base inaqueous solution?

A. LiHB. CaH2C. H2D. KH

-68. Which of the following statements is true?

I. NaH is a stronger base than NaOHII. CaH2 is a stronger base than Ca(OH)2

III. HCl is a stonger acid than HClO

A. I onlyB. I and II onlyC. I and III onlyD. I, II, and III

69. Which of the following is a true statement concerningthe reaction:

Ir(aq) + HP(l) ~ H2(g) + OIr(aq)

A. The equilibrium lies to the left because Olf is astronger base than H'.

B. The equilibrium lies to the left because Ir is astronger base than OlF.

C. The equilibrium lies to the right because Oll" is astronger base than H-.

D. The equilibrium lies to the right because H" is a

770. Hydrofluoric acid is a weak acid (PK. = 3.1). In termsof its ionization in water, fluoride is:

A. a weak acidB. a weak baseC. a strong acidD. a strong base

771. What is the acid dissociation constant K. of water?

A. LOx10-14

B. 1.8xlO-16

C. 1D. 10

772. A glass of pure water sits at room temperature. Whichof the following is true?

A. There is about one hydrated H+ for every onebillion water molecules in the glass.

B. There are roughly equal numbers of hydrated Wions and water molecules in the glass.

C. There are roughly equal numbers of hydrated OH-ions and water molecules in the glass.

D. The total number of hydrated H+ ions and Olfions exceeds the total number of water molecules.

773. Which of the following explains why the measured pHof a solution represents an equilibrium condition?

A. The!!.G of an acid-base reaction is negative.B. The Ml of an acid-base reaction is negative.C. The!!.S of an acid-base reaction is positive.D. Proton transfer reactions take place very fast.

774. Given the pK. table below, which of the followingchoices is the strongest base?

Acid oK.HSCN -1.8HBF4 0.5HIO 10.5

A. sewB. BF4-

C. 10-D. CI-

ek_genchem2

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