Version 223 – Exam 2 – mccord – (52125)
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mccord - ch301
— Exam 2 —
Dat Acid
7-9pm Oct 8, 2013
BUR 106
2pm class only - 52125
1
1. Covalent bonding occurs when the octet
rule is satisfied regardless of the potential energy of the shared electrons
2. The potential energy of the shared electrons is independent of the covalent bond,
but the potential energy of the newly formed
molecule is greater than the individual atoms
3. The potential energy of the shared electrons is lower in the bond than it would be
if the electrons were not shared between two
nuclei correct
4. The potential energy of the shared electrons is higher in the bond than it would be
if the electrons were not shared between two
nuclei
c = 3.00 × 108 m/s
h = 6.626 × 10−34 J·s
1 eV = 1.602 × 10−19 J
R = 3.29 × 1015 s−1
R = 2.178 × 10−18 J
7
R = 1.097 × 10 m
−1
me = 9.11 × 10−31 kg
001 3.0 points
Radio station KLBJ broadcasts at a frequency
of 93.7 × 106 s−1 . Determine the length of the
waves that corresponds to this frequency.
Explanation:
Covalent bonds are formed when the potential
energy of the shared pair of electrons is lower
than it would be if the bonds were not formed.
003 2.0 points
Which of the following elements is diamagnetic in its ground state electron configuration?
1. Fe
2. Cl
3. Si
1. 3.20 nm
4. K
2. 2 × 10−8 m
5. Ca correct
3. 3.20 m correct
Explanation:
4. 2 nm
004 3.0 points
Consider an experiment depicting the photoelectric effect. The frequency of the incoming
light is scanned and the resulting kinetic energy of the displaced electrons is measured.
Which of the plots shown (Ek vs ν) is the
correct plot for the data collected during this
experiment?
5. 93.7 m
Explanation:
002 3.0 points
Covalent bonding occurs between atoms when
Version 223 – Exam 2 – mccord – (52125)
Ek
1.
0
correct
ν
0
7. I and II correct
ν
ν
Explanation:
The overfilled 2s subshell violates the Pauli
exclusion principle and the unfilled 2p subshell violates the aufbau principle.
ν
006 3.0 points
Which graph shows the correct trend for ionization energies, IE, of aluminum, Al?
Ek
3.
0
Ek
4.
0
1.
Ek
0
ν
IE
5.
5. I and III
6. II only
Ek
2.
2
Explanation:
The kinetic energy of the displaced electron
scales with the energy of the incoming photon after the threshhold frequency has been
reached.
005 3.0 points
Consider the electron filling diagram
1
2
3
4
5
6
7
8
Number of electrons removed
correct
↑↓ ↑↓ ↑↓
↑↓
↑↓ ↑↓ ↑
↑↑ ↓
↑↓
Which of the following
I) the aufbau principle;
II) the Pauli exclusion principle;
III) Hund’s rule
does it violate?
1. I only
1
2
3
4
5
6
7
8
Number of electrons removed
1
2
3
4
5
6
7
8
Number of electrons removed
3.
IE
3p
3s
2p
2s
1s
IE
2.
2. II and III
3. III only
4. I, II and III
Version 223 – Exam 2 – mccord – (52125)
3
Tetra is the prefix for 4 and hepta is the prefix
for 7, therefore tetraphosphorus heptachloride.
IE
4.
008 3.0 points
Name the ionic compound Ca3 (PO4 )2 , the
major inorganic component of bones.
1
2
3
4
5
6
7
8
Number of electrons removed
1. calcium phosphate correct
2. potassium phosphite
5.
3. tricalcium phosphite
IE
4. chromium phosphate
5. potassium phosooxide
1
2
3
4
5
6
7
8
Number of electrons removed
Explanation:
Al
has
the
electron
configuration
2 2 6 2 1
1s 2s 2p 3s 3p . After three electrons are
removed, the resulting ion, Al3+ , is isoelectric
with neon and has a stable, full octet for its
outer shell. This stable configuration makes it
very hard to remove an electron and we see a
large increase in the energy needed to remove
a fourth electron.
007 3.0 points
What is the name of the compound P4 Cl7 ?
1. potassium(IV) chloride
2. quattrophosphorus sevenchloride
3. tetraphosphorus heptachloride correct
4. tetraphosphorus chlorate
5. phosphorus(IV) heptachloride
6. phosphorus hexachloride
Explanation:
Prefixes for both P and Cl must be used.
6. sodium phosphate
7. calcium phosooxide
Explanation:
Ionic compound names follow the convention: cation name followed by the anion name.
009 3.0 points
The quantum mechanical approach to atomic
structure permits the calculation of
1. the most probable distance between any
two specified electrons.
2. the number of electrons in an atom.
3. the most probable radius of an orbit that
an electron of specified energy will follow.
4. the most probable spin value that will
be associated with an electron of specified
energy.
5. a region about the nucleus in which an
electron of specified energy will probably be
found. correct
Explanation:
According to the Heisenberg Uncertainty
Principle, the momentum and the position
of an electron cannot both be known simula-
Version 223 – Exam 2 – mccord – (52125)
taneously with any accuracy. The quantum
mechanical approach attempts to calculate
the energy of the electron exactly by defining
possible energy states for the electron. The
position of the electron cannot then be known
with any certainty. Instead, a region of space
around the nucleus is identified in which the
electron is likely to be. These regions of space
are commonly known as orbitals.
010 3.0 points
What is the subshell notation and the number of orbitals that can have the quantum
numbers n = 5, ℓ = 2?
4
Rank the following diatomic molecules by
bond energy, from greatest to least: F2 , N2 ,
O2 .
1. F2 > O2 > N2
2. N2 > O2 > F2 correct
3. Not enough information.
4. F2 > N2 > O2
5. N2 > F2 > O2
Explanation:
1. 5 s; 2
012 3.0 points
Which of the following compounds would be
expected to have the shortest bonds?
2. 5 d; 5 correct
3. 5 p; 5
1. CCl4
4. 5 d; 7
2. NO2 − correct
5. 5 p; 7
3. NO3 −
6. None of these
ℓ value
letter
0
s
1
p
2
d
3
f
4
g
5
h
mℓ = −ℓ, −(ℓ − 1), −(ℓ − 2), · · · , 0, · · ·
+(ℓ − 2), +(ℓ − 1), +ℓ
1
and ms = ± .
2
To find the number of orbitals that can have
the stated values of n and ℓ (and any allowed
values of mℓ and ms ), use ℓ to find the number
of different values of mℓ .
To find the maximum number of electrons
that can have the stated values of n and ℓ
(and any allowed value of mℓ and ms ), double
the number of different values of mℓ .
011
3.0 points
4. NCl3
Explanation:
triple bonds < double bonds < single
bonds. The more bonds, the shorter the bond
length. Resonance structures have bonds
somewhere between single and double bonds.
The more bonding atoms sharing the 2 electrons, the weaker the bond and the longer the
−
bond length. NO−
2 and NO3 are both resonance structures, but NO−
2 has fewer bonding
atoms. Therefore it has stronger bonds, and
shorter bond lengths.
013 3.0 points
Which of the following is the correct Lewis
structure of hydroxylamine (NH2OH)?
H
b
b
Explanation:
The notation is nℓ where
n = 1, 2, 3, 4, 5, · · ·
ℓ = 0, 1, 2, · · · , (n − 1) represented by a letter:
1.
N
O
H
H
b
b
Version 223 – Exam 2 – mccord – (52125)
5
The Lewis formula for hydrogen cyanide
(HCN) is
H C N
H
b
b
b
b
b
b
2.
N
O
015 3.0 points
How many lone pairs are in the Lewis Dot
structure for the chlorite ion ClO−
2?
H
H
H
b
b
1. 2
b
b
3.
b
b
N
O correct
2. 6
H
H
3. 8 correct
H
4.
H
O
N
4. 0
5. 3
H
6. 4
Explanation:
7. 1
014 3.0 points
Which of the following is the correct Lewis
formula for hydrogen cyanide (HCN)?
Explanation:
The Lewis
for the chlorite ion
 Dot structure
−
b b
H
C
b
b
N
b b
b
b
b b
H
C
ClO−
2
N
b b
b b
4.
5.
b
b
b
b
b
b
b
b
b
b b
C
N
b b
b b
b b
b b
b b
b b
H
C
N
b b
b b
b b
b b
b b
b
H
C
N
C
N
b
b
C
N
b
b
b b
b b
016 0.0 points
This question starts out at zero points but
could very well increase after the grading.
Now, if more points are awarded (the curve)
on this assignment, would you like them
added to your score?
b
b
b
bb
b b
6.
b
b
H
b b
7.
H
8.
H
N
b b
b b
bb
9.
b
b
b
b
bb
H
C
N
b b
b b
b b
H
C
N
bb
10.
C
b b
Explanation:
bb
b b
b
b
b
b
H
b b
Cl 
 .

O
b
b
3.
b
b
b
b
b
2.
 O
is 

b
b
b b
b
b
b
b
b
b
b b
1.
8. 5
b
b
correct
1. NO, leave my score alone, I prefer the
lower score
2. YES, I would like the points and the
higher score. correct
Explanation:
This should be a no-brainer. Most students
want higher scores. If you picked yes, you got
credit for the question and you got the extra
points you asked for (if they were granted
by your instructor). If you answered NO,
Version 223 – Exam 2 – mccord – (52125)
you also got what you wanted... no points
awarded.
6
Which substance has ionic bonds?
1. H2 O
017 3.0 points
The carbon-oxygen bonds in the ClCO2 − ion
have the (same/different) bond strengths and
the (same/different) bond lengths. Note: carbon is the central atom.
2. CaO correct
3. O2
4. OF2
1. different, different
2. same, different
3. same, same correct
Explanation:
020 3.0 points
Consider the following pairs A and B
b b
4. different, same
Explanation:
ClCO2 − has two resonance structures. The
C–O bonds have an average bond order
of 1.5, therefore they will have the same
length/strength.
018 3.0 points
The first and second excited states for hydrogen atoms occur at -3.40 eV and -1.5 eV, respectively. An electron located in the ground
state (-13.6 eV) interacts with a 1046 nm photon. What might happen to the electron? (1
eV = 1.6022 x 10−19 J)
1. The electron could be excited from the
ground state to the 1st energy level.
2. The electron could be excited from the
1st energy level to the 2nd energy level.
3. The electron could be excited from the
ground state to the 2nd energy level.
4. The electron will remain in the ground
state. correct
Explanation:
A 1046 nm photon corresponds to an energy
of 1.9 x 10−19 J. The electron will not have
enough energy to move to the first excited
state. It will remain in the ground state.
019
3.0 points
b b
N
A1 )
N
b b

b
b


B1 ) 
O

b b
O
b b
b
b


O 


b b
b b
P
b b
b
b
b b
O
3−
O
b b
N
b
b


B2 ) 
O

N
b b
O
O
3−
b
b
b b
b
b
b b
b
b
b b
b
b
b
b
A2 )



O


b b
P
b b
b
b
O
b b
b
b
b b
of Lewis structures.
Select the one from each pair that is likely
to make the dominant contribution to a resonance hybrid.
1. A1 and B1
2. A2 and B1 correct
3. A2 and B2
4. A1 and B2
Explanation:
b b
A1 )
b b
N
N
O
−1
+1
0
b b
b b
b b
b
b
A2 )
N
N
O
0
+1
−1
b
b
b b
The second structure is preferred because it
places the negative formal charge on the most
electronegative atom.
3−


3−
O −1
O −1

 0
0




−1 
0


B2 ) 
B1 ) 
 O P O
O P O 



−1
0
O
−1 O
−1
b
b
b b
b
b
b
b
b b
b b
b b
b b
b
b
b
b
b b
b
b
b b
b b
b b
b b
b
b
b
b
b b
b
b
b b
The first structure is preferred for the same
reason.
021
3.0 points
Version 223 – Exam 2 – mccord – (52125)
A low-pressure mercury-vapor lamp has a
characteristic emission line at 253 nm. Knowing that this lamp is putting out 11.8 watts
of light energy, how many mercury atoms are
emitted per second during operation?
1. 1.08 x 1017 atoms
2. 5.25 x 1020 atoms
3. 7.86 x 10−19 atoms
4. 1.50 x 1019 atoms correct
5. 7.11 x 1024 atoms
5
6. 4.73 x 10 atoms
Explanation:
c
3 x 108
ν= =
= 1.186 x 1015 s−1
λ
253 x 10−9
E = hν = (6.626 x 10−34)(1.186 x 1015)
= 7.857 x 10−19 J/photon
11.8 W = 11.8 J/photon and for 1 second =
11.8 J
11.8 J
= 1.50 x 1019 photons or atoms
7.857 x 10−19
of Hg
022 3.0 points
There is a series of lines in the hydrogen
line spectrum known as the Paschen series.
One of those lines has a wavelength of 1.28
µm. Which transition between principle levels (n) shown below corresponds to this emission event?
7
Explanation:
1.28 µm means that λ = 1.28 x 10−6 m and
therefore ν = 2.34 x 1014 s−1 .
ν
2.34 x 1014
1
1
=
= 0.07124 = 2 − 2
15
ℜ
3.29 x 10
n2
n1
The fact that the line is in the infra-red region
means that the emission must be due to the
transition to the n=3 level (definition of the
Paschen series). There are only 2 choices with
the n=3 as the final state, 5 → 3, or 5 → 2.
1
1
5 to 2: −
= 0.21 which is too big, as are
4 25
all transitions to levels 1 or 2.
1 1
= 0.071 which matches up with
5 to 3: −
9 25
the previous calculation.
023 3.0 points
You would expect a carbon-oxygen bond to
be
1. polar, with the carbon end having a partial negative charge.
2. nonpolar, with the neither end having a
partial charge.
3. nonpolar, with the oxygen end having a
partial negative charge.
4. nonpolar, with the carbon end having a
partial negative charge.
5. polar, with the oxygen end having a partial negative charge. correct
1. 3 → 1
6. polar, with neither end having a partial
charge.
2. 5 → 3 correct
Explanation:
3. 4 → 3
024 3.0 points
Which of the following molecules does not
obey the octet rule?
4. 8 → 2
5. 5 → 2
1. AsI5 correct
6. 2 → 1
2. NBr3
Version 223 – Exam 2 – mccord – (52125)
8
4. Electrons having the same kinetic energy
would be ejected, but there would be less of
them.
3. CO2
4. SiO2
5. PCl3
Explanation:
AsI5 has five iodine atoms surrounding the
central As atom. This structure does not obey
the octet rule because As has ten electrons
surrounding it.
025 3.0 points
The amount of energy required to convert one
mole of an ionic solid to its gaseous ions is
called
1. attractive forces energy.
2. crystal lattice energy. correct
3. kinetic energy.
4. potential energy.
Explanation:
In the process, the strong electrostatic
forces holding the cations and anions together
are overcome and the particles move away and
are independent cations and anions; e.g.,
+2
MgCl2 (s) −→ Mg (g) + 2 Cl (g)
∆H = crystal lattice energy
5. Electrons having the same kinetic energy
would be ejected, but there would be more of
them.
Explanation:
Intensity is related to the number of photons. Each photon can, if it has sufficient energy, cause one electron to be ejected. Since
the intensity is not changing, the number of
photons is constant and the number of electrons ejected will not change.
Wavelength is inversely proportional to the
energy of the photon. A shorter wavelength
indicates a higher energy photon. The kinetic
energy of the ejected electron is the energy
absorbed from the photon minus the energy
needed to escape the metal surface (the work
function). An electron absorbing a higher
energy photon will have have more energy left
over after escaping the surface and will thus
have a higher kinetic energy.
027 3.0 points
A diatomic molecule decomposes by the following reaction:
X2 → X+ + X−
−
026 3.0 points
The work function for calcium, Ca, is 2.90 eV.
When I shine light of a certain wavelength and
intensity on the calcium surface, electrons are
ejected. What would happen if I changed the
light shining on the calcium surface to have
the same intensity but a shorter wavelength?
Look carefully at the following pictures.
Which one accurately depicts this reaction
as it is proceeding?
+
-
-
1.
+
+
1. Electrons would still be ejected, but they
would have a lower kinetic energy.
+
2. No electrons would be ejected.
3. Electrons would still be ejected, but they
would have a higher kinetic energy. correct
-
-
2.
3.
+
+
correct
-
Version 223 – Exam 2 – mccord – (52125)
the photons is high enough to eject an electron
from a chemical bond or free atom.
+
-
-
4.
+
+
5.
9
-
+
Explanation:
Cations are smaller than their parent neutral atoms while anions are large than the
parent neutral atom.
030 3.0 points
Consider the experiment shown below, in
which a sample of gas phase argon atoms
is excited with electricity and the resulting
electromagnetic radiation is passed through
a prism. Which best describes the spectrum
you would expect to see as a result of this
experiment?
028 3.0 points
Identify which pair of species below are isoelectronic.
Detector
1. P−3 and Cl
Argon
2. Kr and Br
−1
correct
3. Ne and Ar
4. S−2 and Se−2
5. H+ and He
Explanation:
Kr and Br− both have 36 electrons each,
which means they are isoelectronic. All the
other pairs are not isoelectronic.
029 2.0 points
X-rays are dangerous because
1. They are not dangerous because they are
scattered off the surface of your skin.
2. They are not dangerous as they pass
straight through your body.
3. They cause the molecules inside cells to
become very hot.
4. They have high energy photons capable
of ionizing molecules. correct
Explanation:
X-rays are dangerous because the energy of
1. A continuous spectrum.
2. Mostly black space with thin lines of color.
correct
3. A continuous spectrum broken by thin
black lines.
Explanation:
In this experiment, all light reaching the detector is being emitted by the argon atoms as
electrons in these atoms fall from higher to
lower energy levels. The energy of these emitted photons must correspond to the difference
in energy between the two levels. Because energy levels are quantized – only specific energies are permitted – there will be only specific
gaps between energy levels. Therefore we get
only specific thin lines of color emitted, rather
than a continuous spectrum.
031 3.0 points
Increasing wavelength of light goes in the order
1. visible, ultraviolet, infrared
Version 223 – Exam 2 – mccord – (52125)
2. infrared, visible, ultraviolet
3. visible, infrared, ultraviolet
4. ultraviolet, infrared, visible
5. ultraviolet, visible, infrared correct
10
atomic radius increases because the shielding
effects of inner electrons reduces the effective
nuclear charge experienced by outer shell electrons. As you move across the periodic table
the radius decreases because electrons are being added to the same electronic shell (and
thus do not add additional shielding effects)
while the number of protons increases.
6. infrared, ultraviolet, visible
Explanation:
Ordered by wavelengths,
ultraviolet < visible < infrared
032 3.0 points
Compared to a 280 nm photon, a 320 nm
photon has:
1. longer wavelength, higher frequency,
higher energy
2. shorter wavelength, lower frequency,
lower energy
3. shorter wavelength, higher frequency,
lower energy
4. longer wavelength,
higher energy
lower frequency,
5. shorter wavelength, lower frequency,
higher energy
034 3.0 points
Which has a stronger carbon-oxygen bond,
carbon monoxide or carbon dioxide?
1. carbon monoxide correct
2. they are equal strength in both compounds
3. carbon dioxide
Explanation:
The C-O bond in carbon monoxide (CO) is
stronger as it is a carbon/oxygen triple bond.
In carbon dioxide (CO2 ) the carbon/oxygen
bond is a double bond.
035 3.0 points
Which of the atoms and ions given will have
the smallest radius?
1. F
2. Ca+2
6. longer wavelength, lower frequency, lower
energy correct
Explanation:
033 3.0 points
Which atom is smaller?
1. They have the same size.
2. bromine correct
3. iodine
4. Unable to determine
Explanation:
As you move down the periodic table
3. Na+ correct
4. Al
5. C
6. O−2
Explanation:
The Al, Ca+2 both have electrons in principle level 3 and thus are larger than those in
principle level 2. Of the 4 listed that are in
level 2, Na+ has the greatest effective nuclear
charge (+9) and therefore is the smallest.