Version A: Instructions: Write down your Version on the
front page of your exam or you will lose 10 points
Midterm is worth 47 points, not including extra credit, which gives you up to 14 extra points.
RIGHT NOW- fill in your ID number, the bubbles and your version letter on the answer sheet, do
this now so you don’t forget.
There are four versions of the exam. The questions are designed to look similar yet give you the
wrong answer if yo ucopy. If you copy, you are most likely copying the wrong answer, this
makes cheating even more pointless than normal, please don’t do it.
If you think someone nearby may be copying, or something is simply disturbing you, please let
me know and we can adjust people’s seats appropriately. Tell me as early as possible.
Be sure to sign the sign in sheet. This is my record that you attended the class. If you are not
sitting in your assigned seat for a reason approved by me, you’ll need to make sure to write the
seat where you are actually sitting next to your name.
You will also need to show your ID to the TA when you turn in your exam.
Only the answer sheet will be graded. You may (and should) keep the exam sheet. Go
home, retake it, see how you did . If you write any work on scrap paper, the question sheet or
anywhere other than the space given, it will not be graded and you will not get any credit for it.
Do not write on the back of the sheets, do not write anything you want graded anywhere other
than the space given. I’d suggest writing in pencil or doing scratch work elsewhere and then
copying over.
Use your time wisely. Do problems you know first, do problems worth many points first.
Exams will be sent through eee dropbox. They will be graded the same day as you take it, and
the grades will be posted at least by the next morning, if not sooner. It will take a week or more
to get the exams back to you depending on how backed up the system is. I can’t make this go
faster, it is completely out of my hands.
Finally, relax. At that point there is nothing that being stressed will do for you. So take a
deep breath, pick up your writing utensil and show me how amazing you are at
chemistry!
Did you write down your version letter: if not do so now or you will lose
points.
Long Answer Problems- Partial Credit Allotted, please show your work on the answer sheet to receive
partial credit. Make sure you have written down your version letter on the answer sheet front page.
Question 1 (5 points)- Draw the Lewis structure for ClF4+ and ClF4- . What is the electron geometry,
molecular geometry, and bond angles?
ClF4+ = electron geometry: trig bipyramidal, molecular geometry: see saw, bond angles <120 and <90
ClF4- = electron geometry: octahedral, molecular geometry: square planar, bond angles 90
Question 2 (6 points)- Draw the MO diagram for CO. Assume that 2p is lower in energy than 2p. Be sure to
label all atomic and molecular orbitals, including subscripts. Be sure to fill in all electrons necessary. What is
the bond order?
See book for diagram. Bond order =3,
Points marked off for the following: missing atomic labels, missing E with arrow axis label, missing sigma/pi
labels, missing subscripts on sigma/pi labels, flipped ordering of sigma_2p and pi_2p orbitals
Question 3 (3 points)- Describe the difference between bonding and anti-bonding orbitals. Address how
they are formed, energy levels and which are filled first.
Bonding orbitals are formed by constructive interference (adding wavefunctions) while antibonding are
formed by destructive interference (or subtracting wavefunctions). Antibonding orbitals are higher in energy
and therefore bonding orbitals are filled first.
Question 4 (5 points)- Here is the basic outline of an MO diagram for O2. Is it
paramagnetic or diamagnetic, explain? What is the bond order? What is the
bond order of O2-? What is the Bond order of O2+?
Paramagnetic, 2, 1.5, 2.5
Question 5 (4 points).
A) Which has the higher boiling point- butane, (C4H10) or pentane (C5H12)? Why?
Pentane: more electrons or larger electron cloud so there are more dispersion
forces
B) Which has the higher boiling point- ethanol (C2H5OH) or 1,2-diethanol
(HOCH2CH2OH)? Why?
More hydrogen bond donors and acceptors (saying more dispersion forces isn’t
wrong however it doesn’t give the main reason so you wouldn’t get full points
for it here)
Bonus Question (points given on quality of answer): Pick one of the following 2 questionsWhere in nature is hydrogen bonding important?
What makes a molecule a greenhouse gas? Give some examples that show the different ways this can occur?
Short Answer Problems- No partial credit allotted, be sure to round to proper significant figures, include all
units and check for calculation mistakes. All answer must be on the line in the answer sheet. No work will be
graded. Please do all work on scrap paper in the back of this packet. Put only your answer on the sheet. (2
points each)
1. Draw the Lewis structure of HCN
2. Draw the Lewis structure of BF3
3. What is the hybrization of BF3?
Sp2
4. What is the bond angles of BF3?
120
5. True or False: XeCl44+ has the same electron geometry as XeCl4.
false
6. True or False: H2S has the same electron geometry as H2O.
true
7. What is the molecular formula of the following? (one bonus point if you can name it).
HO
OH HO
O
HO
OH
glucose
C6H12O6: glucose
Use the following molecule to answer number 8
and 9. (a bonus point if you can name it, put your
name in the blank for number 8)
Use the following for questions 10-12.
O
O
O
10. Is the molecule polar?
yes
11. What is the bond angle?
<120
12. What is the hybridization.
Sp2
8. What is the hybridization of the circled Carbon?
Sp2; cocaine
9. What is the hybridization of the circled
Nitrogen?
Sp3
Use the following for questions 13 -15.
13. Is the molecule polar?
no
14. What is the bond angle?
109.5
15. What is the hybrization?
Sp3
16. Rank the following molecules (A, B and C) in
order of increasing bond angles.
Molecule A has: Electron Geometry: Trigonal
planar,
Molecular Geometry: Bent
Molecule B has: Electron Geometry: Tetrahedral
Molecular Beometry: Bent
Molecule C has: Electron and Molecular Geometry:
Trigonal Planar
B<A<C
17. Which orbital does hydrogen use to bond to
carbon in CH4?
s
18. Which orbital does the sp3 hybridized carbon
use to bond with in H3CCOH?
Sp3
19. Which orbital does carbon use to from a 
bond in H3CCOH?
p