Name:_ _l_<_e_'f_ _ __
7 Dec 2013 Prof. Urban SC111 Exam 4 Chapters 9-11, Expt 30 A
1. Draw the complete Lewis structure for each of the following. (6 points)
o (, C­
1-\ 3)( t :;.. ?>e -
-
-
t-\ -O-K
-
t-\
•• 1"
~e-
,
\
~t-
••
!/lil
~
••
••
" IJ'
-tJ\.,.A'
l
.,
..
• I' O •
• \..A •
2. The following Lewis structures mayor may not be correct. If the Lewis structure is incorrect or
incomplete, redraw the correct one. If the Lewis structure is correct, write CORRECT in the box.
(9 points)
Lewis Structure
Correct? (If not, draw the corrected one)
S;(p
: F:
f :: 1'1.f.{~2J.
•• I ••
: F-S-F:
.. I ..
'5f(
·.f:
..
: F:
a
H
I"
I
I
H
No!
I
I
H
.. .. ..
H
: F-Be-F:
:0"
I
I'
H­
••
I
\
I
I
t\"
\-\
M-C.-c..-tJ- (-I-\­
H-C-C-N-C-H
H
r\
&. :: 1.eF :. 1-t":fj.
~
,vo!
lflt'"
3. In conducting Experiment 30A, Energy Content of Fuels, a midshipman employed a setup
II}­
consisting of a can containing 100.0 g of water suspended over a fuel lamp containing octane. A
temperature rise in the water of 35.4 °C was measured upon the burning of 1.35g of octane~
~
(CSH18)' Through previous calibration runs the efficiency of the experimental setup was
determined to be 0.425. Use the midshipman's data to determine the fuel value, in kJ/g, for
octane. (5 points) _
=:1»5£1 1
1
fl,,..,..)( It IE£{
;:: ,\Vv,
O
j.
aJ:ue ) (3S.C(
DC)::-
It.f ~"
:r ;:
pf. ~ ~r
I.
~J
4. Draw the three most reasonable resonance structures for the OCN- anion. (C is the central
atom.) (6 points)
(H)
(0)
\:2.)
\~)
:0 -==(.-IV: ~
-
~)
<,:1)
O=-c...:::.N
;.
(-.t:
~
(0)
(0)
:O-C.:E.N:
..
1
tJ-:.. S'e-
ltfMr
IS"e -
s~tr
i/ft)
(f1i>sr ~a."ht. r.1+A(l.6-tTS)
"-'
5,
(}Jof,.. FtJt.I11r't,.
(fLf/l
ICD i-
r1Jtil ,-IF
cltfr{L6-E
Tlt.o"'E? "'r n
vt}"
oN
MilsJ
An M.)
a. Label each atom with its formal charge in each of the resonance structures. (3 points)
b. Rank the three resonance structures from most important (Le., most stable) to the least
important. (Write a 1,2, or 3 under each of the structures. 1 = most stable resonance
structure. 3 least stable resonance structure.) (3 points)
=
5. Use the bond enthalpy values provided below to calculate the reaction enthalpy change(~HrxnO)
in kJ for the reaction below. (8 points)
Bond
CI-CI
H-CI
C-CI
H-C
,*
Bond Enthalpy (kJ/mol)
242.7
431.9
338
414
1+
t{
l
-C - ~
1
-I-
~ -f.).. -? u-
<f lC
<: _/~
o tho (t.Z ,J (E,.d"tk'l (""t) cn­
I.f){ 't I «( ::
If)(
1. '1,-.7
(I - ~
Cf
-I-
K
H-lP
CA.
It
B6"'~
I
(1
I,;)
(! _
l(p $i k,f
O,J () r
u.
H -(1,
:: '170. ~ k,r­
,,~.r
t-",.......
-
1\
or .JI (E~oftt.(i'''''.()
'f ;< -3'3 <l:::::-I 3S"1.'&"1
'1'1.--'" ~1,,-::-'-P..7.lt It!
- 307~. (,
6. Complete the molecular orbital diagrams for He2+ by populating the MOs with electrons to produce the ground-state electron configuration. What is the bond order of He/? Explain in terms of the MO diagram (3 points) Energy
'Bo#lY o(2.J><J1L ;.
(.2
If (.
.0;.
;(
It e .t -;:.
)..
(~j,~_
Bo-Ib,,Jv €
I
L
'l, -
t..f.( -
~
-I ':. 3!­
Sf 1.­
l
7. Consider the molecule allene, HzC=C=CH z
a. Indicate the hybridization of each carbon atom.
"L­
lSi/Sf
H2 C=C=CH2
allene
(Per
b. How many sigma and pi bonds are in the molecule?
J
21f
c. Explain which atomic orbitals overlap to form any sigma bonds between carbon atoms
in the molecule.
b~, t,Vu. ft.~ 1rnY'
()r Io;-} ata.. fJv' ~ "c,+\
C- (
tN4lcer
(7
d. Explain which atomic orbitals overlap to form any
. in the molecule.
c.-C 11 blhtds
tCA.l
fM".'o "ridi ~d
-rr
~
1- "P
''$11­
bonds between carbon atoms
r
fl
(d
1l"'~ 1Y"~ ~ 4f 0­
f -ClYh,·f.ls
e. Which of the following pictures best describes the 3-dimensional structure of allene?
Explain your choice.
(10 points)
H
\ c=c=c
/
,
H
A
H""
H
/ ,
H
,!'
'. C=C=C
C=C=C
H-----\,
\
C
H
H
D
H
\
H
P-urh,'-I.t ~ 'P"'- put J'W ,""­
to ~at 1 atm. (8 points)
- Ethanol Data
Molecular Weight
Normal Freezing Point
Normal Boiling Point
Enthalpy offusion
Enthalpy of vaporization
Specific heat of solid
Specific heat of liquid
Specific heat of gas
46.0g/mol
-114·C
78.4 ·C
4.90 kJ/mol
38.6 kJ/mol
2.42 J/g"C
2.44J/"C
1.70J/"C
if'
v
9.
Answer the following questions about the phase diagram shown below. (6 points)
10 20
30 40 50 60 70
T (deg. Celsi"us)
a. Label the normal boiling point on the diagram as point A.
b. Label the normal freezing point on the diagram as point B.
c. Is the solid phase for this substance more or less dense than the liquid? Explain how
you can tell from the phase diagram.
Multiple Choice (3 points each)
10. What is the hybridization of an atom that has three atoms bonded to it and two lone pairs?
a. sp
b. Sp2
c. @
e. .­
Sp3
3
sp d
2
sp 3d
11. What is the formal charge of an oxygen atom that has one double bond to another atom and
two lone pairs?
,..
0==-,...V
~ ~1
II.
c. -1
d. +2
e. -2
12. Which is the best estimate ofthe bond angles in CO/-?
,.a:) 120
0
"1J.
109S c. 180
0
d. Less than 109S
e. Less than 120 0
'?l~~
0 ,.0 - ' -r-o·\';/
. .-"
~
.'
13. Which of the following bonds is most polar?
a. C-H
b. C-N
c. C-C
®
C-O
1_ ..,..~j
"'-1'1'0"'-'
p/~ u
14. The geometry of the CS 2 molecule can best be described as
Iii") Linear
~
b. Bent
c. Trigonal planar
d. Tetrahedral
..
15. Which of the following has polar bonds but is a non-polar molecule?
a. H20 t~
b. F2 ~ C' ~
C9 CF
d.
II'
4
HCI
f
/
I.lJ;IF
')(~.
)a-r
16. Which ofthe following is expected to have the highest boiling point?
o
b.
h
-L-
Br2
q.".ut.e..,f- l-uvJfAA
/fret}
D
c. Ciz
d.
F2
17. Which ofthe following can engage in hydrogen bonding in the liquid state?
a. CHaF
tJ
®
c.
d.
CHaOH
CHaOCHa CHaCHa
C\-\-~o-
H --- ~
- CH '30
18. Which of the following liquids is expected to have the highest viscosity?
HHH
HH
HHHH
I I I
H-O-C-C-C-H
I I I
a.
H H H
I I
H-O-C-C-O-H
I I
(f) H
H
I I I I
H-C-C-C-C-H
I I I I
H H
I
I
I
I
H-C-C-H
c. H H H H
d. H
H
19. Semiconductor chips are made from solid silicon which is a three-dimensional network of silicon
atoms connected to each other by sigma bonds. This is an example of what type of type of
solid?
a.
b.
c.
@
\.
Metallic
Molecular
Ionic
Covalent
~ ~ ~
0
C,."JtJ
~,JA-
20. Which of the following liquid properties are consistent with strong intermolecular forces?
b.
Low vapor pressure at a given temperature ~
Lowboilingpointatagivenatmosphericpre;sure '--- 1.(., (\0
c.
d.
Small heat of vaporization value
All of the above
@
+
I
L J
,,"0 Glf· (.