Download Chem 105 Final Exam

May 3rd, 2012
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Chem 105 Final Exam
There are 50 multiple choices that are worth 3 points each.
There are 4 problems and 1 bonus problem. Try to answer the questions, which you know first,
and then solve the problems, which you are not sure about.
Here is the summary of the total 225 points plus 10 bonus points. Carefully read the questions.
Good luck!
Multiple choices (50 total)
Problems #1
#2
#3
#4
#5 (Bonus)
Total
3 points each, the
total is 150 points
15 points
20 points
15 points
25 points
10 points
235 points
You could use your calculator.
No notes or books of any sort may be used during the exam.
I have neither given nor received aid on the exam.
Signature and date
________________________________________________
1
I. Multiple Choices: (3 points each, 150 total points; Choose the best answer for each
question)
1. Two natures of light are wave and particle. Wave nature means to have _____________ and
particle nature of light is _____________
a) an electric field component and a magnetic field component; quantum
b) an electric field component and a magnetic field component; photon
c) emission and absorption; quantum
d) emission and absorption; photon
Your answer:______________
2. Which of the four quantum numbers (n, l, ml, ms) determines the orientation of an orbital and
which of the four quantum numbers (n, l, ml, ms) determines the shape of an orbital respectively?
a) l; ml
b) ml; n
c) ml; l
d) n; ml
Your answer:______________
3. What is the correct order of the electromagnetic spectrum from shortest wavelength to longest
wavelength?
a) Gamma Rays → X-rays → Ultraviolet Radiation → Visible Light → Infrared Radiation
→ Microwaves → Radio Waves
d) Gamma Rays → X-rays → Visible Light → Ultraviolet Radiation → Infrared Radiation
→ Microwaves → Radio Waves
c) Radio Waves → X-rays → Ultraviolet Radiation → Visible Light → Infrared Radiation
→ Microwaves → Gamma Rays
b) Visible Light → Infrared Radiation → Microwaves → Radio Waves → Gamma Rays →
X-rays → Ultraviolet Radiation
Your answer:______________
4. The maximum number of electrons that can occupy an energy level described by the principal
quantum number, n, is ____________ .
a) n
b) n + 1
c) 2n
d) 2n2
Your answer:______________
5. The first ionization energy is the minimum energy required to remove the first electron from
the atom in its ground state. Which of the following atoms most likely has the highest first ionic
energy?
a) 9F
b) 12Mg
c) 15P
d) 56Ba
Your answer:______________
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6. The hybridization of N in the NH3 molecule is _____________ in which _____________ new
type of orbitals are generated.
a) sp2; 2
b) sp2; 3
c) sp3; 3
d) sp3; 4
Your answer:______________
7. Determine ∆Hºrxn for the reaction 2Al2O3(s) → 4Al(s) + 3O2(g).
You are given: 2Al(s) + (3/2)O2(g) → Al2O3(s), and ∆Hºrxn = –1,670 kJ/mol
a) 835 kJ/mol
b) 1,670 kJ/mol
c) 2,357 kJ/mol
d) 3,340 kJ/mol
Your answer:______________
8. 2.0 L of gas A at 1.00 atm and 1.00 L of gas B at 1.00 atm are combined in a 3.00 L flask. The
flask is sealed and over time they react to completely to give gas C according to the following
chemical equation: 2A(g) + B(g) → C(g). Assume constant temperature condition.
a) 0.33 atm
b) 0.50 atm
c) 0.67 atm
d) 1.0 atm
Your answer:______________
9. A ground-state atom of manganese has __________ unpaired electrons and is ____________.
a) 0, diamagnetic
b) 2, diamagnetic
c) 0, paramagnetic
d) 2, paramagnetic
Your answer:______________
10. Which of the following bonds has the longest bond length and which of the following bonds
has the highest bond energy respectively?
a) C−N; C−N
b) C−N; C≡N
c) C≡N; C−N
d) C≡N; C≡N
Your answer:______________
11. Which one of the following pairs are isoelectronic?
a) Cl- and S
b) K+ and Cl
c) Na+ and K+
d) Zn2+ and Cu+
Your answer:______________
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12. Which of the following substance is/are trigonal pyrimidal?
(i) SO3 (ii) SO32– (iii) NO3– (iv) PF3 (v) BF3
a) only (i) and (ii)
b) only (i), (iii), and (v)
c) only (ii), and (iv)
d) all are trigonal pyrimidal except (v)
Your answer:______________
13. Arrange the following ions in order of increasing ionic radius: Na+, N3–, O2–, F–.
a) F– < O2– < N3– < Na+
b) F– < O2– < Na+ < P3–
c) N3– < O2– < F– < Na+
d) Na+ < F– < O2– < N3–
Your answer:______________
14. Give the number of lone pairs around the central atom and the molecular geometry of AsCl3.
a) 0 lone pair; trigonal planar
b) 1 lone pair; trigonal pyrimidal
c) 2 lone pairs; T shape
d) 3 lone pairs; linear
Your answer:______________
15. The correct order of increasing polarity is _____________ .
a) C-N < C-O < C-F < F-F
b) C-O < C-F < F-F < C-N
c) F-F < C-F < C-O < C-N
d) F-F < C-N < C-O < C-F
Your answer:______________
16. According to the valence shell electron pair repulsion (VSEPR) theory, the geometry of the
SO2 molecule is _____________ and the geometry of the SO3 molecule is_____________
a) linear; trigonal planar
b) linear; trigonal pyrimidal
c) bent; trigonal planar
d) bent; trigonal pyrimidal
Your answer:______________
17. A single pulse of a laser yields an average of 5.00 × 1018 photons with λ = 633 nm. If melting
ice to water at 0°C requires 6.01 kJ/mol, what is the fewest number of laser pulses need to melt
10.0 g of ice? h = 6.63 x 10-34 J·s
a) 2,127
b) 3,343
c) 3,833
d) 38,330
Your answer:______________
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18. What is the maximum number of electrons in an atom that can have the following set of
quantum numbers?
n = 4; l = 3; ml = –2; ms = +1/2
a) 1
b) 2
c) 6
d) 10
Your answer:______________
19. The standard enthalpy change for the following reaction is _____________ .
2C8H18(l) + 17O2(g) → 16CO(g) + 18H2O(l)
given two following reactions:
2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) ∆H° = –11,020 kJ/mol
2CO(g) + O2(g) → 2CO2(g)
∆H° = –566.0 kJ/mol
a) -4,326 kJ/mol
b) -6,492 kJ/mol
c) -10,454 kJ/mol
d) -11,586 kJ/mol
Your answer:______________
20. The enthalpy change for the combustion of one mole of acetylene, C2H2, to form carbon
dioxide and water vapor is -1,010.5 kJ. The reaction is under constant pressure and volume
condition. What is the bond energy of C≡C (BEC≡C) in kJ/mol?
Type of Bonds
Bond Energy (kJ/mol)
C–H
456
C−C
347
C=C
620
C=O
802
O=O
499
O–H
462
a) 799 kJ/mol
b) 962 kJ/mol
c) 1,035 kJ/mol
d) 1,277 kJ/mol
Your answer:______________
21. How many liters of chlorine Cl2 gas at 2.50 x 10 °C and 0.950 atm can be produced by the
reaction of 12.0 g of MnO2 with excess HCl according to the following chemical equation? The
molar mass of MnO2: 86.94 g/mol and the molar mass of Cl2: 70.9 g/mol, R = 0.0821
L·atm/(mol·K). (K = °C + 273)
MnO2(s) + 4HCl(aq) → MnCl2(aq) + 2H2O(l) + Cl2(g)
a) 0.138 L
b) 0.282 L
c) 1.09 L
d) 3.55 L
Your answer:______________
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22. What are the correct numbers of dots surrounding the 33As symbol in the Lewis dot structure
of 33As and surrounding the 33As3- symbol in the Lewis dot structure of 33As3- respectively?
a) 3; 0
b) 3; 6
c) 5; 0
d) 5; 8
Your answer:______________
23. A 125.4 mL sample of 0.2763 M HNO3 is completely neutralized by 352 mL Al(OH)3. What
is the concentration in molarity of Al(OH)3?
3HNO3 + Al(OH)3 Æ Al(NO3)3 + 3H2O
a) 0.0109 M
b) 0.0328 M
c) 0.0984 M
d) 0.295 M
Your answer:______________
24. An aluminum (Al) metal reacts with hydrochloric acid (HCl) to form hydrogen gas (H2) and
aluminum chloride. If the volume of H2 gas is 0.704 L and the pressure of H2 gas is 1.05 atm
after the end of the reaction. Temperature of H2 gas is 22ºC. Calculate how many gram of Al was
used in the reaction. Assuming the percent yield is 100%. R = 0.0821 atm·L/(K·mol)
a) 0.367 g
b) 0.549 g
c) 0.832 g
d) 1.242 g
Your answer:______________
25. Three students (X, Y, Z) are assigned the task of determining the mass of a sample of iron.
Each student makes three determinations with a balance. The results in grams are X (61.5, 61.6,
61.4); Y (62.8, 62.2, 62.7); Z (61.9, 62.2, 62.1). The actual mass of the iron is 62.0 g. Student
_____________ is the least precise and student ____________ is the most accurate.
a) X; Y
b) X; Z
c) Y; X
d) Y; Z
Your answer:______________
26. Ethylene (C2H4) burns in oxygen to form carbon dioxide (CO2) and water vapor. How many
liter(s) of CO2 are obtained from 1.00 liter (L) of O2 at the constant temperature and pressure?
C2H4 + 3O2 → 2CO2 + 2H2O
a) 0.667 L
b) 1.00 L
c) 1.50 L
d) 2.00 L
Your answer:______________
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27. Predict the geometry and polarity of the CS2 molecule.
a) Bent; Nonpolar
b) Bent; Polar
c) Linear; Nonpolar
d) Linear; Polar
Your answer:______________
28. Indicate the type of hybrid orbitals used by the central atom in PF3.
a) sp
b) sp2
c) sp3
d) sp3d
Your answer:______________
29. Use the bond enthalpy data given to estimate the heat released when 50.0 g of propane gas,
C3H8, burns in excess oxygen to yield carbon dioxide and water vapor at 25°C.
Bond Energy (or Enthalpy) (kJ/mol)
Type of Bonds
C−C
347
C≡C
962
O=O
498
C=O
799
O–H
460
C–H
414
a) 1362 kJ/mol
b) 1544 kJ/mol
c) 2248 kJ/mol
d) 2378 kJ/mol
Your answer:______________
30. The Lewis structure for a carbonic ion, CO32-, should show ____ single bond(s), ____ double
bond(s), and ____ lone pair(s).
a) 2, 1, 7
b) 2, 1, 8
c) 3, 0, 7
d) 3, 0, 9
Your answer:______________
31. A chemist wishes to perform the following reaction:
N2 + 3H2 Æ 2NH3
If only 28.2 g of N2 is available, what is the minimum amount, in grams, of H2 needed to
completely react with this quantity of N2?
a) 1.01 g
b) 1.51 g
c) 3.03 g
d) 6.06 g
Your answer:______________
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32. Which of the following ionic solids would have the smallest lattice energy?
a) KF
b) KI
c) LiF
d) NaF
Your answer:______________
33. 18.00 g of glucose (C6H12O6) is dissolved in 0.100 L of water. The molarity (M) of the
glucose solution is _______ . Assume that the final volume of the glucose solution is 0.100 L.
a) 0.0100 M
b) 0.100 M
c) 1.00 M
d) 10.0 M
Your answer:______________
34. Calculate the density in g/L, of CO2 gas at 2.70 x 10 °C and 0.500 atm pressure. R = 0.0821
L·atm/(mol·K). The molar mass of CO2: 44.0 g/mol. (K = °C + 273)
a) 0.893 g/L
b) 1.12 g/L
c) 2.93 g/L
d) 4.02 g/L
Your answer:______________
35. You are given a balanced reaction: 2H2 + O2 → 2H2O. How many moles of water could be
made from 5.0 mol H2 and 3.0 mol O2 at the end of the reaction?
a) 1.5 mol
b) 3.0 mol
c) 5.0 mol
d) 8.0 mol
Your answer:______________
36. What is the oxidation number of S in H2SO4?
a) -2
b) +2
c) +4
d) +6
Your answer:______________
37. What mass of Li3PO4 is needed to prepare 5.00 x 102 mL of a solution having a lithium ion
concentration of 0.175 M?
a) 3.38 g
b) 6.75 g
c) 10.1 g
d) 19.3 g
Your answer:______________
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38. Give the values of all the quantum numbers associated with the electron in 3d shown in the
following diagram.
1s
2s
2p
3s
3p
4s
3d
a) ψ = fn(3, 1, -1, -1/2)
b) ψ = fn(4, 1, -1, -1/2)
c) ψ = fn(3, 2, -2, -1/2)
d) ψ = fn(4, 2, -2, -1/2)
Your answer:______________
39. The correct order of increasing electronegativity is ______________ .
a) As < Ga < K < Cs
b) Cs < K < Ga < As
c) Ga < As < K < Cs
d) K < Ga < As < Cs
Your answer:______________
40. List the following atoms and ions in an order of increasing atomic size: K+, Cl-, Ar, Ca2+, Cl
a) Ar < K+ < Ca2+< Cl < Clb) Ca2+ < K+ < Ar < Cl < Clc) Cl < Cl- < Ar < K+ < Ca2+
d) K+ < Ca2+ < Ar < Cl < ClYour answer:______________
41. According to Bohr’s theory, an electron originally in a higher-energy orbital falls back to a
lower-energy orbital. As a result, a photon is given off. Calculate the wavelength, in nanometers,
of the light emitted by a hydrogen atom when its electron falls from the n = 7 to the n = 4
principal energy level. RH = 2.18 x 10-18 J and h = 6.63 x 10-34 J·s.
a) 1.38 × 10-12 nm
b) 9.18 × 10-7 nm
c) 1.38 × 102 nm
d) 2.17 × 103 nm
Your answer:______________
42. According to Bohr’s theory, an electron originally in a higher-energy orbital falls back to a
lower-energy orbital. As a result, a photon is given off. Calculate the frequency in s-1 (Hz) of the
light emitted by a hydrogen atom during a transition of its electron from the n = 6 to the n = 3
principal energy level. RH = 2.18 x 10-18 J and h = 6.63 x 10-34 J·s.
a) 9.13 × 1013 s-1
b) 2.74 × 1014 s-1
c) 3.65 × 1014 s-1
d) 1.64 × 1015 s-1
Your answer:______________
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43. Valence shell and valence electrons of an atom of tellurium (52Te) are _____________
respectively?
a) 5; 4
b) 5; 6
c) 6; 4
d) 6; 6
Your answer:______________
44. Electrons in an atom have the quantum numbers n = 3, l = 1, ml = 0. Name the orbital in
which these electrons would be found.
a) 3dyz
b) 3py
c) 3dxz
d) 3px
Your answer:______________
45. Give the values of the four quantum numbers of an electron in the orbital of 3d.
a) n: 3; l: -2; ml: -2; ms: +1/2, -1/2
b) n: 3; l: -2; ml: -2, -1, 0, +1, +2; ms: +1/2, -1/2
c) n: 3; l: +2; ml: -2; ms: +1/2, -1/2
d) n: 3; l: +2; ml: -2, -1, 0, +1, +2; ms: +1/2, -1/2
Your answer:______________
46. Which of the following atom and/or ions has/have this electron configuration?
1s2
2s2
2p6
3s2
3p6
4s2
3d5
a) Fe2+ and Co2+
b) Fe2+ and Cu2+
c) Mn
d) Mn and Co2+
Your answer:______________
47. The electron configurations of Zn2+ and Ge are ______________ respectively.
a) 1S22s22p63s23p64s23d8; 1S22s22p63s23p64s23d104p2
b) 1S22s22p63s23p64s03d10; 1S22s22p63s23p64s23d104p2
c) 1S22s22p63s23p64s23d8; 1S22s22p63s23p64s23d64p6
d) 1S22s22p63s23p64s03d10; 1S22s22p63s23p64s23d64p6
Your answer:______________
48. The formal charge of C in HCN is ______________ .
a) -2
b) -1
c) 0
d) +1
Your answer:______________
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49. The total number of lone pair in the NO2– ion is ______________ and the formal charge of N
in the NO2– ion is ______________.
a) 4; -1
b) 4; 0
c) 6; -1
d) 6; 0
Your answer:______________
50. A 2.50-L flask contains a mixture of methane (CH4) and propane (C3H8) at a pressure of 1.45
atm and 20.0°C. When this gas mixture is then burned in excess oxygen, 8.60 g of carbon
dioxide is formed. The other product is water. What is the mole fraction of propane in the
original gas mixture? R = 0.0821 L·atm/(mol·K)
a) 0.148
b) 0.344
c) 0.656
d) 0.852
Your answer:______________
II. Problem Solving
1. Show all the resonance forms of HNO3. Calculate the formal charges for N atom and three O
atoms in all the resonance forms of HNO3. Show your calculations for the formal charges of any
one of the resonance forms of HNO3. (Total 15 points and showing the calculation is 4 points)
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2. Write Lewis structures for the following molecules. (20 points, 4 points each)
(a) CH4O2
(b) H3PO4
(c) CO
(d) C2H5Cl
(e) CH4N2O
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3. Draw the dipole moment for each bond and the resultant dipole moment if not zero, for the
following molecules. Specify whether each molecule is nonpolar or polar. Justify your answers.
(15 points, 5 points each)
(i) CH4
(ii) SO2
(iii)H2O
4. When a 0.952 g sample of an organic compound CxHyOz containing C, H and O is burned in
completely in oxygen, 1.35 g of CO2 and 0.826 g of H2O are produced. What is the empirical
formula of the compound? Show your calculations. (25 points)
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5. Bonus question (total 10 points). IT IS GREAT TO KNOW YOU! I BELIEVE YOU HAVE
TRIED YOUR BEST IN THIS COURSE! HAVE A GOOD WINTER BREAK! BEST WISHES!
(a) What is the molar concentration of chloride ions in a solution prepared by mixing 50.0 mL of
2.00 M KCl with 100.0 mL of a 1.50 M CaCl2 solution? Assume the final volume is additive.
Show your calculations or justify your answer. (5 points)
(b) Show the Lewis structure of N2O and calculate the formal charges on the two nitrogen atoms
and one oxygen atom in N2O? Show your calculations. (5 points)
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