Question 1

Which of the following statements about the packing of monatomic solids with different unit cells is incorrect?

Accepted Answer

A)  The coordination number of atoms in hcp and fcc structures is 12.
B)  The coordination number of atoms in simple cubic structures is 6.
C)  The coordination number of atoms in bcc structures is 8.
D)  A bcc structure has a higher packing efficiency than a simple cubic structure.
E)  A bcc structure has a higher packing efficiency than a fcc structure.F) All of the above
G) A) and E) E

Question 2

Lead crystallizes in the face-centered cubic lattice.What is the coordination number for Pb?

Accepted Answer

A)  4
B)  6
C)  8
D)  10
E)  12F) A) and B)
G) C) and D)

Question 3

Consider the following phase diagram and identify the process occurring as one goes from point C to point D.

Accepted Answer

A)  increasing temperature with a phase change from solid to liquid
B)  increasing temperature with a phase change from solid to vapor
C)  increasing temperature with a phase change from liquid to vapor
D)  increasing temperature with no phase change
E)  increasing temperature beyond the critical pointF) A) and E)
G) None of the above

Question 4

Hexagonal close packing of identical atoms occurs when close-packed layers are stacked in an abcabc....arrangement.

Accepted Answer

A) True 
 B)False

Question 5

In metals,the conduction bands and valence bands of the molecular orbitals are separated by a large energy gap.

Accepted Answer

A) True 
 B)False

Question 6

Which of the following liquids is likely to have the highest surface tension?

Accepted Answer

A)  Br2
B)  C8H18
C)  CH3OCH3
D)  CH3OH
E)  PbF) All of the above
G) C) and E)

Question 7

Which of the following atoms should have the greatest polarizability?

Accepted Answer

A)  F
B)  Br
C)  Po
D)  Pb
E)  HeF) A) and B)
G) A) and C)

Question 8

Which of the following statements concerning a face-centered cubic unit cell and the corresponding lattice,made up of identical atoms,is incorrect?

Accepted Answer

A)  The coordination number of the atoms in the lattice is 8.
B)  The packing in this lattice is more efficient than for a body-centered cubic system.
C)  If the atoms have radius r,then the length of the cube edge is  8 \sqrt 88c-2.7,0,-7.17,-2.7,-13.5,-8c-5.8,-5.3,-9.5,-10,-9.5,-14c0,-2,0.3,-3.3,1,-4c1.3,-2.7,23.83,-20.7,67.5,-54c44.2,-33.3,65.8,-50.3,66.5,-51c1.3,-1.3,3,-2,5,-2c4.7,0,8.7,3.3,12,10s173,378,173,378c0.7,0,35.3,-71,104,-213c68.7,-142,137.5,-285,206.5,-429c69,-144,104.5,-217.7,106.5,-221l0 -0c5.3,-9.3,12,-14,20,-14H400000v40H845.2724s-225.272,467,-225.272,467s-235,486,-235,486c-2.7,4.7,-9,7,-19,7c-6,0,-10,-1,-12,-3s-194,-422,-194,-422s-65,47,-65,47zM834 80h400000v40h-400000z'/>​   ×	imes×  r.
D)  There are four atoms per unit cell in this type of packing.
E)  The packing efficiency in this lattice and hexagonal close packing are the same. F) A) and B)
G) C) and D) A

Question 9

The energy of a hydrogen bond is greater than that of a typical covalent bond.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following should have the highest boiling point?

Accepted Answer

A)  CF4
B)  CCl4
C)  CBr4
D)  CI4
E)  CH4F) A) and E)
G) C) and D)

Question 11

A metal such as chromium in the body-centered cubic lattice will have _______________ atom(s) per unit cell.

Accepted Answer

A)  1
B)  2
C)  3
D)  4
E)  9F) A) and E)
G) None of the above

Question 12

The phase diagram for xenon has a solid-liquid curve with a positive slope.Which of the following is true?

Accepted Answer

A)  Solid xenon has a higher density than liquid xenon.
B)  Solid xenon has the same density as liquid xenon.
C)  The phase diagram cannot be used to predict which phase of xenon is denser.
D)  Freezing xenon is an endothermic process.
E)  None of these statements is true.F) A) and D)
G) C) and D)

Question 13

For the solid forms of the following elements,which one is most likely to be of the molecular type?

Accepted Answer

A)  Xe
B)  C
C)  Pb
D)  S
E)  CrF) A) and C)
G) A) and E)

Question 14

Assuming that atoms are spherical,calculate the fraction of space which is occupied by atoms (i.e. ,the packing efficiency)in a metal with a simple cubic unit cell.

Accepted Answer

The answer of Assuming that atoms are spherical,calculate the fraction...

Question 15

The density of solid sodium chloride,NaCl,is 2.17 g/cm3.Use your knowledge of the sodium chloride lattice to calculate the spacing between Na+ and Cl- nearest neighbors,in cm.(Atomic masses (amu)are: Na,22.99;Cl,35.45.Also,1 amu = 1.661 $\times$ 10-24 g)

Accepted Answer

2.82 $\times$ 10^-8 cm

Question 16

Comparing the energies of the following intermolecular forces on a kJ/mol basis,which would normally have the highest energy (i.e. ,be the strongest force) ?

Accepted Answer

A)  ion-induced dipole
B)  dipole-induced dipole
C)  ion-dipole
D)  dipole-dipole
E)  dispersionF) All of the above
G) D) and E)

Question 17

Select the pair of substances in which the one with the higher vapor pressure at a given temperature is listed first.

Accepted Answer

A)  C7H16,C5H12
B)  CCl4,CBr4
C)  H2O,H2S
D)  CH3CH2OH,CH3-O-CH3
E)  Xe,KrF) C) and D)
G) A) and E)

Question 18

Neon condenses due to

Accepted Answer

A)  dipole-dipole forces.
B)  London dispersion forces.
C)  hydrogen bonding.
D)  covalent bonding.
E)  intramolecular forces.F) A) and E)
G) B) and C)

Question 19

A temperature increase causes __________________ in the conductivity of a semiconductor.

Accepted Answer

A)  a decrease
B)  an increase
C)  a modulation
D)  an increase or decrease (depending on the semiconductor) 
E)  no changeF) A) and B)
G) All of the above

Question 20

A cubic unit cell has an edge length of 400.pm.The length of its body diagonal (internal diagonal) in pm is therefore

Accepted Answer

A)  512
B)  566
C)  631
D)  693
E)  724F) A) and C)
G) A) and E)

Exam 12: Intermolecular Forces: Liquids,solids,and Phase Changes

Which of the following statements about the packing of monatomic solids with different unit cells is incorrect?

Correct AnswerverifiedE

Lead crystallizes in the face-centered cubic lattice.What is the coordination number for Pb?

Correct AnswerverifiedShow Answer

Consider the following phase diagram and identify the process occurring as one goes from point C to point D.

Correct AnswerverifiedShow Answer

Hexagonal close packing of identical atoms occurs when close-packed layers are stacked in an abcabc....arrangement.

Correct AnswerverifiedShow Answer

In metals,the conduction bands and valence bands of the molecular orbitals are separated by a large energy gap.

Correct AnswerverifiedShow Answer

Which of the following liquids is likely to have the highest surface tension?

Correct AnswerverifiedShow Answer

Which of the following atoms should have the greatest polarizability?

Correct AnswerverifiedShow Answer

Which of the following statements concerning a face-centered cubic unit cell and the corresponding lattice,made up of identical atoms,is incorrect?

Correct AnswerverifiedA

The energy of a hydrogen bond is greater than that of a typical covalent bond.

Correct AnswerverifiedShow Answer

Which of the following should have the highest boiling point?

Correct AnswerverifiedShow Answer

A metal such as chromium in the body-centered cubic lattice will have _______________ atom(s) per unit cell.

Correct AnswerverifiedShow Answer

The phase diagram for xenon has a solid-liquid curve with a positive slope.Which of the following is true?

Correct AnswerverifiedShow Answer

For the solid forms of the following elements,which one is most likely to be of the molecular type?

Correct AnswerverifiedShow Answer

Assuming that atoms are spherical,calculate the fraction of space which is occupied by atoms (i.e. ,the packing efficiency)in a metal with a simple cubic unit cell.

Correct AnswerverifiedShow Answer

The density of solid sodium chloride,NaCl,is 2.17 g/cm3.Use your knowledge of the sodium chloride lattice to calculate the spacing between Na+ and Cl- nearest neighbors,in cm.(Atomic masses (amu)are: Na,22.99;Cl,35.45.Also,1 amu = 1.661 ×\times× 10-24 g)

Correct Answerverified2.82 \(\times\) 10-8 cm

Comparing the energies of the following intermolecular forces on a kJ/mol basis,which would normally have the highest energy (i.e. ,be the strongest force) ?

Correct AnswerverifiedShow Answer

Select the pair of substances in which the one with the higher vapor pressure at a given temperature is listed first.

Correct AnswerverifiedShow Answer

Neon condenses due to

Correct AnswerverifiedShow Answer

A temperature increase causes __________________ in the conductivity of a semiconductor.

Correct AnswerverifiedShow Answer

A cubic unit cell has an edge length of 400.pm.The length of its body diagonal (internal diagonal) in pm is therefore

Correct AnswerverifiedShow Answer

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The density of solid sodium chloride,NaCl,is 2.17 g/cm³.Use your knowledge of the sodium chloride lattice to calculate the spacing between Na⁺ and Cl^- nearest neighbors,in cm.(Atomic masses (amu)are: Na,22.99;Cl,35.45.Also,1 amu = 1.661 $\times$ 10^-24 g)

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2.82 \(\times\) 10^-8 cm

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