Chemistry for Engineers Homework Answers - Chapter 8

Chapter 8 Homework Questions

The surface tension of a liquid is greater in liquids with strong intermolecular forces.

  True

  False

Band gaps tend to be largest for:

1.	conductors
2.	insulators
3.	semiconductors
4.	modulators

Give the number of atoms in the unit cell. Assume the structure consists of identical atoms.

face-centered cubic

a.	one
b.	two
c.	four
d.	eight

Which of the following substances would exhibit dipole-dipole intermolecular forces?

a.	BCl3
b.	CF4
c.	CO2
d.	Cl2
e.	NH3

Which compound-solid type pair is not correctly matched?

1.	NaOH - ionic solid
2.	carbon (diamond) - amorphous solid
3.	carbon (graphite) - layered solid
4.	H2O (ice) - molecular solid
5.	Mg (elemental form) - metallic solid

Iridium metal exhibits a cubic closed packed solid structure so coordination number of each Ir atom in the solid is 6.

True

False

Which of the following has the highest boiling point?

a.	N2
b.	CH2Cl2
c.	LiF
d.	SiH4
e.	impossible to tell without more information

The boiling points of the noble gases increase going down the group. What type of intermolecular force best accounts for this fact?

	a.	permanent dipole moment
	b.	ion-ion
	c.	hydrogen bonding
	d.	London dispersion
	e.	dipole-dipole

The reason that some insects can walk on water is due to

	a.	vaporization.
	b.	surface tension.
	c.	cohesive forces.
	d.	dishwashing detergent.
	e.	capillary action.

The boiling points of the halogens increase going down the group. What type of intermolecular force best accounts for this fact?

a.	permanent dipole
b.	ion-ion
c.	hydrogen bonding
d.	London dispersion
e.	ion-dipole

A property of metals that is explained by the sea-of-electrons model is their ductility.

  True

  False

Surface tension represents a net force of attraction between molecules on the surface of a liquid and molecules in the        Bulk       .

The action of Sulfur (element name) in the vulcanization of natural rubber results in cross-linking of the polymer strands.

Intramolecular forces refer to the bonding forces within a molecule. Choose which forces are involved in this change.

those allowing liquid benzene to crystallize when cooled

a.	intramolecular
b.	intermolecular
c.	both
d.	neither

Choose the strongest interparticle force in this substance.

Kr

a.	dipole-dipole
b.	dispersion
c.	H-bonding
d.	ionic bonds
e.	dipole-induced diploe

Which of these statements is FALSE?

a.	Metallic solids usually exhibit completely filled bands and completely empty bands separated by large energy gaps
b.	Partially occupied valence bands usually lead to a solid behaving as a metallic onductor of electric current
c.	Overlap of the energies of fully occupied and empty valence bands can result in the solid having metallic character
d.	If the highest filled band is separated by a large energy gap from the next band which is vacant, the solid will behave as an insulator
e.	If the highest filled band is separated by a only a small energy gap from the next band which is vacant, the solid will behave as an semiconductor

Dacron is an example of a(n) ______ because it is made up of more than one type of monomer. copolymer

Copper crystallizes in a face-centered cubic lattice. How many copper atoms are there per unit cell?

a.	1
b.	2
c.	4
d.	8
e.	12

Which notion is incorrect?

	a.	Dispersion forces are present in all molecular substances.
	b.	The greater the dipole moment, the stronger the dipole-dipole forces.
	c.	Hydrogen bonding is an intermolecular force that only occurs in certain types of molecules.
	d.	Polar molecules always have stronger overall intermolecular forces than nonpolar molecules.
	e.	Hydrogen bonding leads to the strongest intermolecular forces.

Which of these materials provides an example of a molecular crystalline solid?

1.	SiC
2.	V2O5
3.	NaBr
4.	Al

Iridium metal exhibits a cubic closed packed solid structure so the 4th layer in the solid is identical to the first layer.

True

False

Which set of the following statements contains all the true statements and none that are false?

A. CCl₄ has a greater polarizability than CF₄

B. CH₃OH has a lower intermolecular forces than CH₃CH₃

C. CH₃CH₂CH₂CH₃ has a smaller London forces than C₆H₁₄

a.	A only
b.	B only
c.	C only
d.	A and C only
e.	none of these

Choose the type of crystal lattice this metal forms. (The number of atoms per unit cell is given in parentheses.)

Ni (4)

a.	simple
b.	face-centered
c.	body-centered
d.	hexagonal

Which set of these statements is FALSE?

i) Electrical conductivity of an alkali metal results from the movement of electrons in the partially filled conduction band

ii) Silicon doped with Al would act as a p-type semiconductor

iii) electrical conductivity in p-type semiconductors is attributable to the movement of positive "holes"

a.	i) only
b.	ii) only
c.	iii) only
d.	i) and iii) only
e.	all are True

The synthesis of a copolymer with one continuous "core" strand of the first monomer with attached strands of the second monomer creates a(n):

1.	graft copolymer
2.	anti-polymer
3.	alternating copolymer
4.	block copolymer

Which of the following statements is true about p-type silicon semiconductors?

a.	It is produced by doping Si with P or As.
b.	It does not conduct electricity as well as pure Si.
c.	Electrons are the mobile charge carriers.
d.	All are true.
e.	None is true.

A p-type semiconductor

	a.	is made by doping host atoms with atoms having one more valence electron than the host.
	b.	is made by doping host atoms with atoms having one fewer valence electron than the host.
	c.	has electrons that lie close in energy to the conduction bands.
	d.	has electrical conductivity that increases as its temperature decreases
	e.	has somewhat lower electrical conductivity that its pure host solid

When the pressure over a liquid is decreased, the boiling point of the liquid will

a.	always decrease.
b.	always increase.
c.	increase or decrease.

For which of the following is hydrogen-bonding not an important intermolecular force?

a.	H2O
b.	CH3NH2
c.	HF
d.	BH3
e.	CH3CH2OH

Intramolecular forces refer to the bonding forces within a molecule. Choose which forces are involved in the following change.

those allowing fog to form on a cool, humid evening in Houston

a.	intramolecular
b.	intermolecular
c.	both
d.	neither

Non-metals have large band gaps and do not conduct electricity.

1.	True
2.	False

Which of the following substances represents an excellent conductor of electricity?

1.	zinc
2.	silicon
3.	iodine
4.	sucrose

Which statement is not correct?

a.	A volatile liquid has a high boiling point.
b.	The boiling point of a liquid is the temperature at which its vapor pressure is equal to the external pressure.
c.	The stronger the intermolecular forces, the higher the boiling point.
d.	The equilibrium vapor pressure above a liquid is independent of the volume of liquid present and the volume of vapor present.
e.	The vapor pressure above a liquid increases with temperature.

Give the number of atoms in the structure. Assume each structure consists of identical atoms.

body-centered cubic

a.	one
b.	two
c.	four
d.	eight

Metal bonding models including the sea of electron model. In this model the valence electrons of the metal atoms are separated by water molecules, and hydrogen bonding with these water mediators provides many of the metallic properties we observe.

1.	False
2.	True

Water doesn't "wet" waxed paper because its (1.)_Cohesive (or) Adhesive forces are stronger than the (2.) Cohesive (or) Adhesive_ forces between the hydrocarbons making up the wax and the water molecules. 

The ability to bend a metallic solid is described by the metal's:

1.	mobility
2.	ductility
3.	malleability
4.	polymeric breakpoint

Semiconductors have small band gaps between their filled valence bands and their vacant conduction bands.

Predict the effect (if any) of an increase in temperature on the electrical conductivity of each material.

semiconductor

a.	conductivity increases with increasing temperature
b.	conductivity decreases with increasing temperature
c.	conductivity increases then decreases with increasing temperature
d.	conductivity does not change with temperature

For the following substances, choose the answer which best describes

what type of solid will form, respectively.

NaOH HCl CaO Sn

	a.	ionic, network, molecular, metallic
	b.	ionic, molecular, ionic, metallic
	c.	network, molecular, ionic, network
	d.	network, molecular, ionic, metallic
	e.	none of these

According to the sea-of-electrons model the metal's Valence  electrons move freely through the solid metal leading to electrical conductivity.

One polymorph of tin has a fcc unit cell. If the atomic radius of Sn is 141 pm, what is the volume of a tin unit cell in cm³?

	a.	7.93 x 10-24
	b.	6.34 x 10-23
	c.	2.80 x 10-24
	d.	2.24 x 10-23
	e.	3.97 x 10-24                                      {(4(1.41x10^-8cm))/sqrt2}^3=ans