CHEMISTRY 120
Name:_______________________
I.D. #___________________
D.Klapstein
December 2011
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This is a two (2) hour exam.
Read over the entire exam before beginning.
Ration your time according to the value of each question.
There should be 37 different questions in this exam. If your exam copy does not contain 37 different questions notify the
instructor immediately.
Answer Part I (questions 1 - 30) on the multiple choice answer card. Use a black pencil to indicate your answer; press
firmly on the pencil to leave a dark mark indicating your answer. Be sure to put your NAME, I.D. number and
COURSE on the multiple choice answer card.
Answer Part II (questions 31 - 37) in the space provided. Be sure to put your NAME and I.D. number on the exam.
At the end of the exam, hand in BOTH the multiple choice answer card and the exam. It is your responsibility to
insure that your answers are legible.
READ ALL QUESTIONS CAREFULLY
A Periodic Table is found at the end of the exam questions. Other useful data:
1 standard atmosphere = 760.0 mm Hg = 101.325 kPa.
Avogadro's Number = 6.022 × 1023
Universal gas constant R = 0.08206 L atm/(K mol)
= 62.37 mm Hg L/(K mol)
= 8.3144 L kPa/(K mol)
= 8.3144 J /(K mol)
Ideal gas law: PV = nRT
Heat capacity of water: 4.184 J g-1 C-1
Density of water: 1.00 g/mL
For E.M. radiation, E = h = hc/
Standard molar volume = 22.414 L
Speed of light c = 2.9979  108 m s-1
Planck's Constant h = 6.626  10-34 J s
charge on an electron = 1.602  10-19 C
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Part I. Multiple Choice. 1 mark each. Be sure to mark your answer on the card IN PENCIL
1. A single atom of an unknown element has a mass of 2.339824  10-22 g. Assuming that the element has only one
naturally occurring isotope, the element must be
a. La
b. Ce
c. Pr
d. Nd
e. none of these
2. How many hydrogen atoms are present in 3.41 g of NH3 ?
a. 2.89 x 1022 atoms
b. 1.20 x 1023 atoms
c. 2.41 x 1023 atoms
d. 3.62 x 1023 atoms
3. The outermost electrons of an atom determine most of its chemistry because those electrons are
a.
b.
c.
d.
e.
more negatively charged due to their distance from the center.
more shielded from the effects of approaching atoms.
more strongly affected when other atoms approach.
All of these are correct.
None of these are correct.
4. Which of the following compounds is an example of an alkaline earth halide?
a. CaF2
b. LiBr
c. FeCl3
d. SrO
e. none of these
5. The oxidation number of the sulfur atoms in S4O62- is
a. -2
b. +4
c. +5/2
d. +3
e. +2
6. The positive charge on the nucleus of an atom is numerically equal to the
a. atomic mass
b. atomic number
c. mass number
d. all of these
e. zero
7. Choose the incorrect statement concerning electromagnetic radiation.
a. Infrared light has a longer wavelength than ultraviolet light.
b. The greater the frequency of the electromagnetic radiation, the greater the energy of the radiation.
c. A photon with a wavelength of 5000 Ångstroms has one-half as much energy as a photon with a wavelength of
2500 Ångstroms.
d. The speed of ultraviolet light rays is faster than x-rays in a vacuum.
e. Electromagnetic radiation is energy transmission in which electric and magnetic fields are propagated as waves.
Chemistry 120 Exam – December 2011
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8. An element M is a main-group metal that reacts with oxygen to give the compound M2O. If the metal forms a
chloride that is 21.06% Cl (by mass), the element must be
a. Sr
b. Rb
c. Na
d. Cs
e. none of these
9. Why is the electron affinity so positive for the noble gas elements?
a. The added electron would have to go into a new shell.
b. The added electron would have to be added into the half-filled p subshell.
c. The added electron would have to be added into the p subshell.
d. The noble gas elements are diatomic elements.
e. Electrons can't be added to gases.
10. An ionic compound that dissolves in water with a sizable proportion of its ions still associated would be called
a. a non-electrolyte.
b. a weak electrolyte.
c. a strong electrolyte.
d. a saturated electrolyte.
11. If the temperature of a sample of an ideal gas remains constant while the pressure is decreased by a factor of three,
the volume must
a. increase by a factor of three.
b. decrease by a factor of three.
c. increase by a factor of less than three.
d. decrease by a factor of less than three.
12. If the formula of an oxide is X2O3, what is the formula of the chloride of X?
a. XCl
b. X3Cl
c. XCl3
d. XCl6
e. X2Cl3
13. Which one of the following statements is not true concerning the equation below?
N2 + 3 H2  2 NH3
a.
b.
c.
d.
H = - 459.0 kJ
the reaction of a mole of nitrogen uses up 459 kJ of heat
the reaction of 3 moles of hydrogen produces 459 kJ of heat
the production of a mole of ammonia is accompanied by the production of 229.5 kJ of heat
complete reaction of 0.8278 mole of hydrogen requires 0.2759 mole of nitrogen
14. Which comparison of ionization energies is correct?
a. Cs > Na
b. Na > Mg
c. Ca > Mg
d. Ca+ > Ca
e. Ar > He
15. The pressure of 450 mL of a gas is 1.00 atm. If the volume is reduced until the pressure of the gas is 5.00 atm, the
resulting volume will be
a. 75.0 mL
b. 90.0 mL
c. 450 mL
d. 2.25 L
16. What mass of argon is contained in an 18.6 L container at 20.0C if the pressure is 2.35 atm?
a. 21.9 g
b. 72.6 g
c. 322 g
d. 1.06 kg
17. Which of the following subshells is correctly designated?
a. 1p5
b. 3s3
18. The density of H2S at STP is
a. 0.658 g L-1
b. 1.52 g L-1
c. 3f 2
d. 4d11
c. 22.4 g L-1
e. 2p6
d. 34.1 g L-1
19. Consider a piece of metal with light striking its surface causing the photoelectric effect. As the intensity of the light
increases,
a. the kinetic energy of the ejected electrons increases
b. the number of ejected electrons increases
20. Sigma () bonds are:
a. always present in double bonds
b. formed only by p orbitals
c. formed only by hybrid orbitals
c. the number of ejected electrons decreases
d. the kinetic energy of the ejected electrons decreases
d. formed only by s orbitals
e. formed only by unhybridized orbitals
21. Which one of the following has the highest first ionization energy?
a. C
b. B
c. O
d. N
22. The element with the electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 is
a. Ca
b. Be
c. Cl
d. K
23. Which of the following is an amphoteric oxide?
a. Al2O3
b. Li2O
c. PO3
d. Sc2O3
e. SrO
24. Which of the following is a bent (nonlinear) molecule?
a. CO2
b.CS2
c. BeF2
d. OF2
e. none - all are linear
Chemistry 120 Exam – December 2011
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25. Which of the following statements concerning quantum numbers is NOT correct?
a. "n" relates the most probable distance from the nucleus.
b. "l" denotes geometric shape.
c. "m" denotes orientation of an orbital with respect to the others.
d. The fourth quantum number refers to electron spin.
e. The four quantum numbers are derived from wave mechanics.
26. What mass of KNO3 in grams will be required to prepare 0.150 L of a 0.675 molar solution?
a. 4.50 g
b. 6.98 g
c. 10.2 g
d. 68.2 g
e. none of these
27. If a solution containing 4.000 g of NaOH is exactly neutralized by 80.00 mL of an aqueous HCl solution, the
molarity of the HCl solution must have been
a. 0.001250 M
b. 0.001370 M
c. 1.250 M
d. 1.370 M
e. none of these
28. If gas volume is doubled but the temperature remains constant:
a. the pressure stays the same
d. the molecules move slower
b. the molecules move faster
e. none of these answers
c. the kinetic energy increases
29. The angular momentum quantum number  is related to
a. the size of the orbital
b. the shape of the orbital
c. the electronic spin
d. the number of orbitals in the shell
e. the pH
30. The stable isotopes of chlorine are designated 35Cl and 37Cl. The numbers 35 and 37 are referred to as
a. atomic masses
b. molar masses
c. mass numbers
d. abundance indeces
e. isotope numbers
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PART II. ANSWER ALL OF THE FOLLOWING PROBLEMS IN THE SPACE PROVIDED. EACH
QUESTION HAS A VALUE OF 10 MARKS
31. The power ratings of microwave ovens are listed in watts (1 watt = 1 J/s).
(a) How many seconds will it take a microwave oven rated at 750 watts to warm 575 mL of soup from 25ºC to
85ºC? Assume that the heat capacity and the density of the soup are the same as that of water.
(b) If the frequency of the microwaves is 2450 MHz, what is the wavelength of the microwaves?
(c) How many moles of photons of microwave radiation are absorbed by the liquid in part (a)?
32. Elemental analysis of an organic liquid with a fishy odor gives the following elemental mass percentages: 14.94% H;
71.22% C; and 13.84% N. Vaporization of 250. mg of the compound in a 150. mL bulb at 150º C gives a pressure of
435 torr.
(a) What is the molecular formula of the compound?
(b) Provide a reasonable structure, clearly showing all atom connectivities, consistent with your formula.
33. Using the concepts of electron group geometries, predict the formula of the molecule or ion that contains a tellurium
(Te) atom and a number of fluorine atoms so that the molecular or ion shape is (a) bent; (b) T-shaped; (c) square
pyramid; (d) trigonal bipyramid; (e) octahedron; and (f) seesaw. Summarize your results in the bottom table.
Shape:
bent
T-shaped
square
pyramid
trigonal
bipyramid
octahedron
seesaw
Formula:
34. (a) It requires 496 kJ/mol to break O2 molecules into atoms and 945 kJ/mol to break N2 molecules into atoms.
(i) Explain why these two energies are so different.
(ii) Calculate the maximum wavelength (in nm) of light that can break each of these molecules apart.
(b) Sulfur trioxide has no dipole moment, but arsenic trifluoride (AsF3) has  = 2.59 D. Use Lewis structures to
account for this difference in dipole moments.
Chemistry 120 Exam – December 2011
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35. Cinnamic acid is one of the components of natural cinnamon oil. Describe the hybridization of the atoms labeled A,
B, C, D, and E. What are the bond angles about atoms A, C, D, and E? How many -bonds does the structure have?
How many -bonds? Put your answers in the following table.
A
B
H
H
C
C
C
A
C
E
B
C
O
H
H
H
H
Atom
C
C
C
H
O
H
C
D
C
C
D
E
Hybridization
Bond angle
Number of
-bonds
Number of
-bonds
36. (a) Dilithium molecules Li2 can be generated by vaporizing lithium metal at very low pressure. Do you think it is
possible to prepare diberyllium Be2? Explain your reasoning using MO diagrams for Li2 and Be2.
(b) Describe the bonding in SO2 in terms of orbital overlap and delocalized electrons.
37. (a) Although xenon (Xe) is a ‘noble gas’, it forms a few compounds with fluorine and oxygen. In one reaction, when
xenon gas reacts with F2 gas, XeF4 is the product. If 5.00 g of xenon reacts with excess fluorine and generates
4.00 g of XeF4, what is the percent yield of the reaction and how much xenon remains unreacted, assuming no
other product forms?
(b) One common component of antacids is Mg(OH)2. If an upset stomach contains 125 mL of 0.115 M HCl (typical
values), what mass of Mg(OH)2 is required to completely neutralize the acid?
The End – Happy Holidays!