chemistry, the central science , 10th edition

Donna Narsavage HealdSiena CollegeLoudonville, NY 2006, Prentice-Hall

Midterm ReviewNuclear Chemistry

Gas LawsIntermolecular ForcesColligative PropertiesChemical Equilibrium

Chemistry, The Central Science, 10th edition

Theodore L. Brown, H. Eugene LeMay, Jr., and Bruce E. Bursten

What change in the mass number of a nucleus occurs when the nucleus emits an alpha particle?

1. Mass number decreases by 1.



4. Mass number does not change.

1. Yes

2. No

Bonus:

1. Alpha rays most efficiently pass through the window.

2. Beta rays most efficiently pass through the window.

3. Gamma rays most efficiently pass through the window.

Indicate the number of protons (p) and neutrons (n) in the radioactive nucleus represented by: 60

27 Co1. 60 p, 27 n2. 33 p, 27 n3. 27 p, 33 n4. 27 p, 60 n5. None of the above

Correct Answer:

1. 60 p, 27 n2. 33 p, 27 n3. 27 p, 33 n4. 27 p, 60 n5. None of the above

The difference between the mass number and the atomic number is the number of neutrons (60 27) = 33.

If the nucleus:

undergoes positron emission it will become the isotope:

1. Potassium392. Argon383. Argon394. Calcium385. Calcium39

3819 K

Correct Answer:

The nuclear equation describing this process is given below:

3819 K

01 e

3818 Ar +

1. Potassium392. Argon383. Argon394. Calcium385. Calcium39

Which of the following nuclei would you expect not to be radioactive? A band of stability is provided for reference.

1. Carbon-142. Phosphorus-313. Iron-594. Radium-2265. Uranium-235

Correct Answer:

Only phosphorus-31 is not outside the band of stability; its position is indicated by the red arrow.

1. Carbon-142. Phosphorus-313. Iron-594. Radium-2265. Uranium-235

How many (X) neutrons are required to balance the nuclear transmutation equation shown below?

1. 12. 23. 34. 45. 6

nXKrBaUn 10

9136

14256

23592

10

Correct Answer:

1. 12. 23. 34. 45. 6

n3KrBaUn1

0

91

36

142

56

235

92

1

0

The balanced nuclear equation is given below:

The isotope carbon-14 has a half-life of 5,715 years. How much of a 1.00 g sample of carbon-14 will exist after 34,290 years?

1. 0.0156 g2. 0.0225 g3. 0.143 g

4. 0.166 g5. None (all would have

decayed).

Correct Answer:

1. 0.0156 g2. 0.0225 g3. 0.143 g4. 0.166 g5. None (all would

have decayed).

34,290 yr/5,715 yr = 6

Thus, six half-lives occur over this time.

1.00 g ( ) 6 = 1.00 g (1/64) = 0.0156 g1 2

1. Loss of a neutron.2. Gain of a proton.3. Loss of electrons.4. Loss of an alpha particle.5. Gain of a positron.

The radioactive decay of Ra to Rn occurs with:

226Ra 222Rn

Oxygen-15 is used as a radioactive tracer in medical imaging and has a half-life of 2.0 min. If the initial

concentration of 15O is 16 mM, how long will it take for the concentration to be reduced to 1 mM?

1. 4 min2. 6 min3. 8 min4. 10 min5. 12 min

If 250 mL of NO is placed in a flask with O2, what volume of O2 is needed for complete reaction?

1. 100 mL2. 125 mL3. 200 mL4. 250 mL5. Cannot be determined from the given information.

2 NO (g) + O2 (g) 2 NO2 (g)

If equal masses of CH4, C2H6, and C3H8 are placedin a flask, which of the following is true?

1. PCH4 = PC2H6

= PC3H8

2. PCH4 ~ PC2H6

~ PC3H8

3. PCH4 > PC2H6

> PC3H8

4. PCH4 < PC2H6

< PC3H8

5. None of the above

1. Gases are generally of very low molecular mass.

2. Gases have high kinetic energies.

3. In gases, the distance between molecules is relatively large.

4. In gases, the attractions between molecules are large.

1. Densities cannot be compared without additional amount and volume information.

2. Water vapor has the same density as N2 under

the same conditions of temperature and pressure.

3. Water vapor is less dense than N2.

4. Water vapor is more dense than N2.

1. Additional pressure information is needed to compare average kinetic energies.

2. The heaviest gas (HCl) has the highest average kinetic energy and the other average kinetic energies decrease with molar mass.

3. HCl (298 K) and H2 (298 K) have the same

average kinetic energy while O2 (350 K) has a

lower average kinetic energy.

4. HCl (298 K) and H2 (298 K) have the same

average kinetic energy while O2 (350 K) has a

higher average kinetic energy.

1. Gases deviate from ideal behavior if their molar mass exceeds that of H2O.

2. Gases deviate from ideal behavior if the temperature is lower than room 298 K.

3. Gases deviate from ideal behavior because the molecules have finite sizes and there are some attractions between the molecules.

4. Gases deviate from ideal behavior if their normal boiling points are below room temperature and greater than the freezing point of H2O.

A gas initially at 2.0 atm is in an adjustable volume container of 10. L in volume. If the pressure is decreased to 0.50 atm, what is the new volume?

1. 40. L2. 20. L3. 10. L4. 5.0 L

Correct Answer:

PV

1constant

constantPV

Thus,

2.00 atm(10. L) = 0.50 atm (Vfinal)Vfinal = 2.00 atm(10. L)/0.50 atm = 40. L

1. 40. L2. 20. L3. 10. L4. 5.0 L

Assuming pressure is held constant, to what volume will a balloon initially at 1.0 L change if its temperature is decreased from 300 K to 75 K?

1. 1.0 L2. 2.0 L3. 0.25 L4. 4.0 L

Correct Answer:

TV constant

constantT

V

Thus,

1.0 L/300 K = (Vfinal)/75 KVfinal = 75 K/(1.0 L)300 K = 0.25 L

1. 1.0 L2. 2.0 L3. 0.25 L4. 4.0 L

At standard temperature and pressure, how many moles of gas are present in a box with a volume of 112 L?

1. 1.00 moles2. 2.00 moles3. 5.00 moles4. 0.200 moles

Correct Answer:

L 22.41

atm 1.000

K 273.15KL·atm/mol· 0.08206mol 1

P

nRTV

nRTPV

Thus, at STP

22.41 L = 112 L1.00 mol n

n = 5.00 moles

1. 1.00 moles2. 2.00 moles3. 5.00 moles4. 0.200 moles

A container holds a mixture of oxygen, neon, and helium gases whose partial pressures are 150 torr, 300 torr, and 450 torr, respectively. The mole fraction of neon is

1. 0.172. 0.333. 0.504. 0.67

totali PP i

Correct Answer:

Xi = Pi/Ptotal

Xi = (300 torr)/(150 + 300 + 450) torr

Xi = 300 torr/900 torr = 0.33

totali PP i1. 0.172. 0.333. 0.504. 0.67

An unknown gas effuses at half the rate of helium. This gas is likely to be which of the following?

1. H2

2. CH4

3. Ne4. O2

5. Ar

1

2

M

M

2

1

r

r

Correct Answer:

(r1/2)2 =M2/M1

M2= (r1/r2)2M1

M2= (2/1)2(4.0 g/mol) = 16.0 g/mol

Therefore it could be CH4

1. H2

2. CH4

3. Ne4. O2

5. Ar

Real gases deviate from ideal behavior at __________ and _________.

1. High temperature; low pressure

2. Low temperature; high pressure

3. High temperature; high pressure

4. Low temperature; low pressure

Correct Answer:

At low temperature and high pressure, intermolecular forces increase as the molecules get closer together.

1. High temperature; low pressure

2. Low temperature; high pressure

3. High temperature; high pressure

4. Low temperature; low pressure

Which of the following molecules can hydrogen bond with itself?

1. 1, 22. 2, 33. 3, 44. 1, 2, 35. 1, 2, 3, 4

CH2F2 NH3 CH3-O-H CH3C CH3

O

1 2 3 4

Arrange the following according to increasing vapor pressure.

1. NH3 < I2 < Br2 < CH4

2. I2 < Br2 < NH3 < CH4

3. NH3 < CH4 < I2 < Br2

4. NH3 < I2 < CH4 < Br2

5. CH4 < NH3 < Br2 < I2

NH3 I2 Br2 CH4

Which statement is true?

1. Boiling point ~120°C2. Boiling point ~95°C 3. Boiling point ~75°C4. Melting point ~95°C5. Melting point ~75°C

0

200

400

600

800

Vap

or

Pre

ssu

re (

mm

Hg

)

25 50 75 100Temperature (° C)

0

Of the following substances, predict which has the highest boiling point based on intermolecular forces.

1. Propane, C3H8

2. Dimethyl ether, CH3OCH3

3. Methyl chloride, CH3Cl4. Acetaldehyde, CH3CHO5. Acetonitrile, CH3CN

Correct Answer:

Each of these molecules has almost the same molecular weight; however, acetonitrile has the largest dipole moment (3.9 D) and hence the largest dipole-dipole forces. Thus it has the highest boiling point.

1. Propane, C3H8

2. Dimethyl ether, CH3OCH3

3. Methyl chloride, CH3Cl4. Acetaldehyde, CH3CHO5. Acetonitrile, CH3CN

Of the following substances, predict which has the lowest boiling point based on London dispersion forces.

1. He2. Ne3. Ar4. Kr5. Xe

Correct Answer:

More massive species have more polarizability and stronger London dispersion forces; consequently, amongst the noble gases He has the lowest boiling point.

1. He2. Ne3. Ar4. Kr5. Xe

Which one of the following phase changes is an exothermic process?

1. Sublimation2. Vaporization3. Condensation4. Melting

Correct Answer:

All the other phase-change processes listed are endothermic.

1. Sublimation2. Vaporization3. Condensation4. Melting

How much energy is required to raise the temperature of 1800. g ice at 0°C to 10°C? Hfus = 6.01 kJ/mol, heat capacity of water is 75.2 J/mol-K.

1. 60.1 kJ2. 75.2 kJ3. 135 kJ4. 601 kJ5. 676 kJ

Correct Answer:

There are 100 moles of ice, so the enthalpy of fusion is:H =(6.01 kJ/mol)(100 mol) = 601 kJ.To raise the water temperature 10°C requires q = (75.2 J/mol-K)(100 mol)(10°C ) = 75.2 kJ. Total energy = 601 kJ +75 kJ = 676 kJ

1. 60.1 kJ2. 75.2 kJ3. 135 kJ4. 601 kJ5. 676 kJ

Temperature

Pre

ssu

reAA

DD

CC

BB

In the unlabeled phase diagram below, the line segment from A to B separates which two phases?

1. Gas-liquid2. Liquid-solid3. Solid-gas

Correct Answer:

1. Gas-liquid2. Liquid-solid3. Solid-gas

Temperature

Pre

ssu

reAA

DD

CC

BB

Diamond and graphite are examples of which type of crystalline solids?

1. Molecular2. Covalent network3. Ionic4. Metallic

Correct Answer:

Diamond and graphite are both forms of carbon, and consist of a network of covalent bonds (hence covalent network).

1. Molecular2. Covalent network3. Ionic4. Metallic

a. gas

1. No comparison can be made between kinetic and attraction energy without temperature information.

2. The average kinetic energy is greater than the energy of attraction.

3. The average kinetic energy is equal to the energy of attraction.

4. The average kinetic energy is less than the energy of attraction.

b. solid

1. No comparison can be made between kinetic and attraction energy without temperature information.

2. The average kinetic energy is equal to the energy of attraction.

3. The average kinetic energy is greater than the energy of attraction.

4. The average kinetic energy is less than the energy of attraction.

1. Ion-dipole forces are encountered in both solutions.

2. Ion-dipole forces are encountered in neither solution.

3. Ion-dipole forces only are encountered in Ca(NO3)2 in water.

4. Ion-dipole forces only are encountered in CH3OH in water.

1. Crystalline solids always melt at a higher temperatures than amorphous solids.

2. Crystalline solids melt at a specific temperature, whereas amorphous ones tend to melt over a temperature range.

3. Amorphous solids always melt at a higher temperatures than crystalline solids.

4. Amorphous solids melt at a specific temperature, whereas crystalline ones tend to melt over a temperature range.

The curve describes the solubility properties of

1. A liquid

2. An ionic solid

3. A covalent solid

4. A gas

5. A gas or liquid0

1.0

2.0

So

lub

ilit

y m

M

15 30 45 60Temperature (° C)

0

Predict which aqueous solution will have the lowest freezing point.

1. 0.25 m C2H5OH

2. 0.15 m CaCl2

3. 0.20 m NaCl

4. 0.15 m NH4NO3

5. 0.15 m Na3PO4

Arrange the aqueous solutions according to increasing boiling point.

1. AlCl3 < KNO3 < Na2SO4

2. Na2SO4 < AlCl3 < KNO3

3. Na2SO4 < KNO3 < AlCl3

4. KNO3 < AlCl3 < Na2SO4

5. KNO3 < Na2SO4 < AlCl3

0.10 m Na2SO4

0.15 m AlCl3

0.20 m KNO3

1. 23 ppm

2. 2.3 ppm

3. 230 ppm

4. 2300 ppm

Determine the mass percentage of hexane in a solution containing 11 g of butane in 110 g of hexane.

1. 9.0 %2. 10. %3. 90.%4. 91 %

Correct Answer:

Thus,

110 g(110 g + 11 g)

100solution of mass total

solution incomponent of masscomponent of % mass

100 = 91%

1. 9.0 %2. 10. %3. 90.%4. 91 %

What is the molality of 6.4 g of methanol (CH3OH) dissolved in 50. moles of water?

1. 0.040 m2. 0.22 m3. 0.064 m4. 0.11 m

Correct Answer:

solvent of kg

solute moles Molality, m

kg/1000g) g/mol)(1 .0 water)(18mol (50

g/mol) (32.0methanol)/ g (6.4m

mm 0.22kg) (0.90

mol) (0.20

1. 0.040 m2. 0.22 m3. 0.064 m4. 0.11 m

How many moles of solute are there in 240 g of a solution that is 5.0% glucose (C6H12O6) by mass?

1. 0.033 moles2. 0.067 moles3. 0.10 moles4. 0.12 moles5. 0.20 moles

Correct Answer:

5.0 % glucose means 5.0 g glucose/100 g solution

(5.0 g glucose/100 g solution)(240 g solution) = 12 g

(12 g glucose) (1 mol glucose/180 g glucose) = 0.067

moles glucose

1. 0.033 moles2. 0.067 moles3. 0.10 moles4. 0.12 moles5. 0.20 moles

Ethanol normally boils at 78.4°C. The boiling point elevation constant for ethanol is 1.22°C/m. What is the boiling point of a 1.0 m solution of CaCl2 in ethanol?

1. 77.2°C2. 79.6°C3. 80.8°C

4. 82.1°C5. 83.3°C

Correct Answer:

The increase in boiling point is determined by the molality of total particles in the solution. Thus, a 1.0 m solution of CaCl2 contains 1.0 m Ca2+ and

2.0 m Cl for a total of 3.0 m. Thus, the boiling point is elevated 3.7°C, so it is 78.4°C + 3.7°C = 82.1°C.

mKT bb

1. 77.2°C2. 79.6°C3. 80.8°C4. 82.1°C5. 83.3°C

Which of the following is not an example of a colloid?

1. Fog2. Smoke3. Paint4. Milk5. Carbonated water

Correct Answer:

Carbonated water is a solution; all the other substances in the list are excellent examples of colloids.

1. Fog2. Smoke3. Paint4. Milk5. Carbonated water

What is Kp in terms of Kc for the following reaction ?

1. Kp = KcRT

2. Kp = Kc(RT)

3. Kp = KcR/T

4. Kp = Kc

5. Kp = Kc/(RT)2

2NO (g) + O2 (g) 2NO2 (g)

What is the correct equilibrium constant expression for the reaction:

P4 (s) + 6Cl2 (g) 4PCl3 (l)

Which accurately reflects the changes in concentration that will occur if O2 is added to disturb the equilibrium?

[NO] [O2] [NO2]

1. Increase Increase Increase

2. Increase Increase Decrease

3. Decrease Decrease Decrease

4. Decrease Decrease Increase

5. Decrease Increase Increase

2NO (g) + O2 (g) 2NO2 (g)

NO NO2

Which of the following will result in an equilibrium shift to the right?

1. Increase temperature/increase volume

2. Increase temperature/decrease volume

3. Decrease temperature/increase volume

4. Decrease temperature/decrease volume

5. None of the above

PCl3 (g) + Cl2 (g) PCl5 (g) H° = -87.9 kJ/mol

PCl5

What is the value of Kc for the reaction?

1. Kc = 1/(5.0 x 1018)1/2

2. Kc = 1/(2.5 x 1018)

3. Kc = -(5.0 x 1018)/2

4. Kc = -(5.0 x 1018)1/2

5. Kc = 2/(5.0 x 1018)1/2

2CO(g) + O2(g) 2CO2(g) Kc = 5.0 x 1018 at 25 °C

CO2(g) CO(g) + 1/2 O2(g) Kc = ?? at 25 °C

For the gas-phase reaction A Bthe forward reaction rate is 3.0 104 s1 and the reverse reaction rate is 1.5 102 s1. What is the value of the equilibrium constant, Keq?

1. 0.022. 503. 0.0004

4. 2500

Correct Answer:

r

fc k

kK

0.021.5x10

3x102-

-4

cK

1. 0.022. 503. 0.0004

4. 2500

1. no bubbles are observed in the reaction mix.

2. the temperature of the reaction mix cools.

3. the concentrations of reactants and products no longer change.

4. the color of the reaction mix remains constant.

1. Kc is 2nd order with respect to NO2 and 1st order with

respect to N2O4.

2. Kc is independent of the starting concentrations of

reactants and products.

3. Kc is 2nd order with respect to NO2 and inversely

related to N2O4.

4. Kc is directly related to NO2 and inversely related to

N2O4.

1. Kp = 1/[H2Og]

2. Kp = PH2O

3. Kp = [H2Og]

4. Kp = 1/PH2O

1. cannot determine without information about energy of reaction.

2. cannot determine without information about reaction rate constant.

3. no.

4. yes.

chemistry, the central science , 10th edition

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mass number

number of neutrons

number of protons p

atomic number

radioactive nucleus

alpha rays

6027co60 p

alpha particle