FOURTH MIDTERM EXAM
Chemistry 101
Professor Vaid
Nov. 19, 2008
Mark all answers on your Scantron answer sheet using a #2 pencil. Fill in your name and
CWID # on the answer sheet.
1. What is the electron configuration of selenium, Se?
A)
B)
C)
D)
E)
[Ar]4s24p4
[Ar]4s23d104p4
[Kr]4s24d104p4
[Ar]3s23d103p4
[Kr]4s23d104p4
2. What is the electron configuration of Sn2+?
A)
B)
C)
D)
E)
[Kr]5s25d105p2
[Kr]5s24d105p4
[Xe]5s24d105p2
[Kr]6s25d10
[Kr]5s24d10
3. How many unpaired electrons are there in a neutral Cl atom?
A)
B)
C)
D)
E)
0
1
2
3
4
4. What is the electron configuration of Cu2+?
A)
B)
C)
D)
E)
[Ar]3d9
[Ar]4s23d9
[Ar]4s23d7
[Ar]4d9
[Ar]4s24d7
5. How many valence electrons does arsenic, As, have?
A)
B)
C)
D)
E)
33
0
5
3
15
1
6. Which of the following elements has the largest atomic radius?
A)
B)
C)
D)
Si
S
Sn
Te
7. Which of the following has the smallest ionic radius?
A)
B)
C)
D)
Ca2+
K+
Cl–
S2–
8. Which of the following has the lowest ionization energy (IE1)?
A)
B)
C)
D)
Be
B
Mg
Al
9. Which 3rd row element has this set of ionization energies?
IE1= 786 kJ/mol IE2= 1,580 kJ/mol IE3= 3,230 kJ/mol
IE4= 4,360 kJ/mol IE5= 16,100 kJ/mol
A)
B)
C)
D)
E)
Al
Si
P
S
Cl
10. In what group (column) of the periodic table do all of the elements have positive, or
endothermic, electron affinities?
A)
B)
C)
D)
E)
1A
2A
5A
7A
8A
11. Which of the following elements is the most metallic?
A)
B)
C)
D)
Si
S
Sn
Te
2
12. Which of the following elements is the strongest oxidizing agent?
A)
B)
C)
D)
E)
K
O2
F2
Br2
Li
13. Which compound would have the largest (most negative) lattice energy?
A)
B)
C)
D)
E)
NaCl
CsCl
BaO
MgO
BaS
14. Lattice energies are not measured directly, but instead determined using the BornHaber cycle and its several other steps with energies that can be determined
experimentally. Suppose that it was found that the ionization energy of sodium is
actually larger than previously thought. How would that affect the magnitude of the
calculated lattice energy of NaCl?
A) it would become larger (more negative)
B) it would become smaller (less negative)
C) it would not change
15. The H+ of a strong acid exists in aqueous solution as H3O+. Draw the Lewis structure
of H3O+. How many lone pairs of electrons are there on the oxygen atom?
A)
B)
C)
D)
E)
0
1
2
3
4
16. Which of the following bonds is the most polar?
A)
B)
C)
D)
E)
C–C
C–O
H–F
K–F
C–F
3
17. The bond length of HF is 92 pm (92 × 10–12 m), and its measured dipole moment is
1.82 D. What is the % ionic character of the H–F bond?
A)
B)
C)
D)
E)
41%
51%
17%
55%
92%
18. Two possible arrangements of neutral NOH3 are:
O
H
N
H
H
H
A
N
H
O
H
B
When the Lewis structures are completed correctly, what are the formal charges on N
and O in structures A and B? Answers below are in the form (F.C. on N, F.C. on O).
A)
B)
C)
D)
E)
A: (0,0)
A: (+1,-1)
A: (-1,-1)
A: (+1,-1)
A: (-1,+1)
B: (+1,-1)
B: (+1,-1)
B: (0,0)
B: (0,0)
B: (0,0)
19. How many reasonable resonance structures are there for [SCN]– (that is the 1- anion,
and the atomic arrangement is as shown, with C the central atom)?
A)
B)
C)
D)
E)
0
1
2
3
4
20. In which molecule or ion will the N-O bonds be the shortest? (N is the central atom)
A) NO2
B) NO2–
C) NO2+
21. Of the anions ClO–, ClO2–, ClO3–, and ClO4– (Cl is the central atom in the latter
three), which has the shortest Cl-O bonds?
A)
B)
C)
D)
ClO–
ClO2–
ClO3–
ClO4–
4
22. In the molecule HNNH (atoms arranged as shown), what is the N-N bond order? (a
single bond has bond order 1, a double bond has bond order 2, etc.)
A)
B)
C)
D)
E)
1
1.5
2
2.5
3
23. In C3H4, how many total C-C bonds are there (single bonds count as 1, double bonds
as 2, etc.)?
A)
B)
C)
D)
E)
2
3
4
5
6
24. The azide anion, N3-, is symmetrical, with the atoms bonded in a linear fashion,
N-N-N. There are 3 important resonance structures. What is the N-N bond order
(single bonds have a bond order of 1, double bonds have a bond order of 2, etc.)?
A)
B)
C)
D)
E)
1
1.5
2
2.5
3
25. Given the following bond energies:
bond
H–H
H–N
N–N
N=N
N≡N
energy (kJ/mol)
436
389
163
418
946
Calculate the enthalpy of the reaction
N2 + 3 H2 → 2 NH3
A)
B)
C)
D)
E)
+1087 kJ
+80 kJ
-608 kJ
+1026 kJ
-80 kJ
5
Information Sheet for Exam 4
Chemistry 101
Professor Vaid
°C = (°F – 32)/1.8
K = °C + 273.15
Avogadro’s number = 6.022 × 1023
Speed of light, c = 3.00 × 108 m/s
Planck’s constant, h = 6.626 × 10-34 J·s
charge on an electron = -1.602 × 10-19 C
1 inch = 2.54 cm
1 foot = 0.305 m
1 mile = 5280 feet
1 mile = 1.61 km
1 gallon = 3.785 L
1 pound = 0.454 kg (at Earth’s surface)
1 atm = 760 torr = 101,325 Pa = 14.70
lb/in2
1 watt (W) = 1 J/s
1 L·atm = 101.3 J
1 J = 1 kg·m2·s-2
1 debye (D) = 3.34 × 10-30 C·m
V = (4/3) π r3 (volume of sphere)
KE = ½ mv2
PV = nRT
2
⎡
⎛n⎞ ⎤
⎢ P + a⎜ ⎟ ⎥ × [V − nb] = nRT
⎝ V ⎠ ⎦⎥
⎣⎢
R = 0.08206 (L·atm)/(mol·K)
R = 8.314 J/(mol·K)
Pa = χaPtotal
v rms =
3RT
M
ΔE = q + w
Nov. 19, 2008
w = F·d
w = -PΔV
q = C·ΔT
q = m·Cs·ΔT
P = F/A
ΔH = ΔE + PΔV
ΔH°rxn = ∑ ΔH°f (products)
- ∑ ΔH°f (reactants)
ΔHrxn = ∑ bond energies (reactants)
- ∑ bond energies (products)
ν·λ = c
E = hν
KEelectron = hν – Φ
(Δx)(m·Δv) ≥ h/4π
En = (-2.18 × 10-18 J)(1/n2)
λ = h/(m·v)
# radial nodes = n - l -1
l = 0, 1, 2, … n-1
ml = - l, - l + 1, - l + 2, … l
μ = q·r
n = 1,2,3,…