Transcript up11_educue_ch42

Q42.1
The difference between an ionic bond and a covalent bond is
1. ionic bonds are only found in crystals such as sodium
chloride (NaCl) where there are many atoms in close
proximity
2. covalent bonds are only found in molecules with three
or more atoms
3. ionic bonds are highly directional, while covalent
bonds are not
4. ionic bonds involve the transfer of an electron from one
atom to another, while covalent bonds involve electrons
that spend much of their time between atoms
A42.1
The difference between an ionic bond and a covalent bond is
1. ionic bonds are only found in crystals such as sodium
chloride (NaCl) where there are many atoms in close
proximity
2. covalent bonds are only found in molecules with three
or more atoms
3. ionic bonds are highly directional, while covalent
bonds are not
4. ionic bonds involve the transfer of an electron from one
atom to another, while covalent bonds involve electrons
that spend much of their time between atoms
Q42.2
When a diatomic molecule rotates very rapidly, the atoms that
comprise the molecule move slightly farther apart (the molecule
“stretches”). What effect does this have on the rotational energy
levels of the molecule?
1. the effect is on the low-energy levels, which are spaced
closer together than if the molecule did not stretch
2. the effect is on the low-energy levels, which are spaced
farther apart than if the molecule did not stretch
3. the effect is on the high-energy levels, which are spaced
closer together than if the molecule did not stretch
4. the effect is on the high-energy levels, which are spaced
farther apart than if the molecule did not stretch
A42.2
When a diatomic molecule rotates very rapidly, the atoms that
comprise the molecule move slightly farther apart (the molecule
“stretches”). What effect does this have on the rotational energy
levels of the molecule?
1. the effect is on the low-energy levels, which are spaced
closer together than if the molecule did not stretch
2. the effect is on the low-energy levels, which are spaced
farther apart than if the molecule did not stretch
3. the effect is on the high-energy levels, which are spaced
closer together than if the molecule did not stretch
4. the effect is on the high-energy levels, which are spaced
farther apart than if the molecule did not stretch
Q42.3
At absolute zero (T = 0 K), what is the difference between
a semiconductor and an insulator?
1. the conduction band is empty in a semiconductor but
partially filled in an insulator
2. the conduction band is partially filled in a semiconductor
but empty in an insulator
3. the energy gap between the valence and conduction
bands is large in a semiconductor but small in an insulator
4. the energy gap between the valence and conduction
bands is small in a semiconductor but large in an insulator
A42.3
At absolute zero (T = 0 K), what is the difference between
a semiconductor and an insulator?
1. the conduction band is empty in a semiconductor but
partially filled in an insulator
2. the conduction band is partially filled in a semiconductor
but empty in an insulator
3. the energy gap between the valence and conduction
bands is large in a semiconductor but small in an insulator
4. the energy gap between the valence and conduction
bands is small in a semiconductor but large in an insulator
Q42.4
If you increase the temperature of a block of copper from 300 K
to 600 K, what happens to the average kinetic energy of the
electrons in the conduction band? (Copper remains a solid at
these temperatures.)
1. the average kinetic energy increases by a factor of 4
2. the average kinetic energy increases by a factor of 2
3. the average kinetic energy increases by a factor of 21/2
4. the average kinetic energy changes by only a small factor
A42.4
If you increase the temperature of a block of copper from 300 K
to 600 K, what happens to the average kinetic energy of the
electrons in the conduction band? (Copper remains a solid at
these temperatures.)
1. the average kinetic energy increases by a factor of 4
2. the average kinetic energy increases by a factor of 2
3. the average kinetic energy increases by a factor of 21/2
4. the average kinetic energy changes by only a small factor
Q42.5
How would you expect the electric conductivity of a
semiconductor to vary with increasing temperature?
1. it should increase, because more electrons are thermally
excited from the valence band into the conduction band
2. it should increase, because more electrons are removed
from their parent atoms and added to the valence band
3. it should decrease, because the added thermal energy
breaks apart correlated electron pairs
4. it should decrease, because the atoms in the crystal will
vibrate more and thus block the flow of electrons
A42.5
How would you expect the electric conductivity of a
semiconductor to vary with increasing temperature?
1. it should increase, because more electrons are thermally
excited from the valence band into the conduction band
2. it should increase, because more electrons are removed
from their parent atoms and added to the valence band
3. it should decrease, because the added thermal energy
breaks apart correlated electron pairs
4. it should decrease, because the atoms in the crystal will
vibrate more and thus block the flow of electrons