FINAL EXAM
Chemistry 121
May 9, 2008
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First
BRING A UNR PICTURE ID TO THE EXAM
Directions: Do not sit next to someone with the same colored exam; circle the correct choice or
fill in the blank, as required and SHOW ALL WORK. Use the blank sheet (in the data
appendix) to cover your work. NO notes, text or other material is allowed for reference on the
exam. No cell phone calls and turn cell phones off. There are 190 total points, but this exam is
scored on the basis of 150 points. Any form of cheating will result in a 0 grade. Problem value
given in [ ].
[10] 1. Give the approximate values for the indicated bond angles and the hybridization the
following molecules:
O
2
(a)
H C
1
N
3
s
_______

hybridization
1. _____
______
2. _____
______
3. _____
______
4. _____
______
5. _____
______
O
Cl H
(b)
H
4
N
5
C
O
[12] 2. What is the designation for the hybrid orbitals formed from the following
combinations of atomic orbitals one s and two p?
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[15] 3. Consider this reaction:
N2(g) + 3H2(g) → 2NH3(g)
At some T and P, 1.2 l of nitrogen reacts with 3.6 l of H2 and all gases are consumed,
that volume of ammonia (same T and P) will be formed?
a)
b)
c)
d)
e)
We need T and P
24.0 l
0.240 l
2.4 l
none of these
[10] 4. Calculate the molar mass (molecular weight) of a vapor that has a density of 7.14 g/l
at 12˚C and 743 torr.
[10] 5. Below are a list of different forces that would cause H2O to liquefy (l) and forces
which would keep water as a vapor (ν). Place an l next to the force(s) leading to
liquefaction and a v next to the force(s) tending to keep H2O as a vapor or neither (n)
if the forces are not present in H2O.
a) hydrogen bonding _________
b) dipole-dipole _________
c) electron repulsion _________
d) ion-dipole _________
e) ion-ion _________
[10] 6. How many core electrons does Mg have? _______
[10] 7. Which area of the periodic table (see below) contains both metal oxy cations and oxy
anions?
a)
b)
c)
d)
The far right-hand side
The far left-hand side
The center
There is no area where both exist
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[18] 8. Using Lewis electron structures (one line to represent a pair of electrons) include
the bonding and lone pair electrons in each of the following resonance structures.
O
O
O
O
C
C
C
O
O
O
O
O
[12] 9. Consider the molecule HNCO; circle all statements below that are correct;
a)
b)
c)
d)
e)
f)
g)
h)
molecule is linear
molecule is planar
molecule is tetrahedral
the H atom has sp hybridization
both C and O are sp2 hybridized
C has 2 pairs of lone pair electrons
The C to O bond has one sigma and one pi bond
HNCO has a dipole moment
[5] 10. Consider HClO4; what is the total number of valence electrons for perchloric acid.
(Circle one)
a) 30
b) 14
c) 32
d) 18
e) none of these
[15] 11. Consider the molecule CS2. It has μD = 0
(a) How many valence electrons does it have?
(i) 16
(ii) 18
(iii) 70
(iv) none of these
(b) What is the hybridization scheme on the carbon atom?
(i) sp3
(ii) sp2
(iii) dsp2
(iv) none of these
(c) How many σ and π bonds does it contain?
_____ σ bonds
_____ π bonds
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[18] 12. Use the scheme below of diatomic molecular orbital assignments (with energy
increasing from bottom to the top of the page), to give the bond order* and magnetic
behavior for each of the following systems. Show all work.
a) LiSi+
B.O.* = ____________
Magnetic description __________________
b) AlC+
B.O. = ____________
Magnetic description __________________
c) FN
B.O. = ____________
Magnetic description __________________
This is the molecular orbital scheme we will use:
σ2*p
π2*p
π2p
σ2p
σ2*s
σ2s
σ1s*
σ1s
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[10] 13. Calculate the number of molecules in a deep breath of air whose volume is 1.55 L at
body temperature, 37°C, and a pressure of 740 torr.
[10] 14. Ammonium sulfate, an important fertilizer, can be prepared by the reaction of
ammonia with sulfuric acid:
2NH3(g) + H2SO4(aq) → (NH4)2SO4(aq)
Calculate the volume of NH3(g) needed at 20°C and 25.0 atm to react with 150 kg of
H2SO4.
[10] 15. Hydrogen gas is produced when zinc reacts with sulfuric acid:
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
If 259 mL of wet H2 is collected over water at 18°C and a barometric pressure of
738 torr, how many grams of Zn have been consumed? (The vapor pressure of water
is tabulated in Appendix B.)
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[15] 16. Here is the isochoric phase diagram for H2O. Match the following numbers
from the list of descriptions found below the diagram.
a) The heat of sublimation on the coexistence line of gas and solid.
Number
b) The boiling point of the liquid, number
c) The critical point (or temperature) where the meniscus of the liquid disappears,
number
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