Hourly
Exam # 3 Dunnivant
Name
(PRINTED)
____________________________________
There
are 100 points. The exam will be
graded on a percentage basis.
The honor statement must be
signed in order for your exam to be graded.
Closed
book, closed Internet, closed notes, closed cell
phone, closed neighbor!
I
have neither given nor received aid on this exam.
Signature
________________________
NOTES: NEATNESS COUNTS AND POORLY DISPLAYED OR
PRESENTED WORK WILL BE DISCOUNTED!!!!!!!!!!!!!
-Show all work for partial
credit.
-CIRCLE FINAL ANSWERS in
math problems
-Significant figures and
units will be graded throughout the exam.
1. (2 pts each) Beside each name below, given the most
significant thing the person did for chemistry or what each theory/equation did
for chemistry: WRITE NEATLY
Neils Bohr (two things)
Edward Schrodinger
The orbital atomic model
(What two things are wrong with the orbital model?)
The quantum-mechanical atomic model
(What is the major limitation of the
quantum-mechanical model?)
Lewis dot structures
VSEPR
(What does VSEPR stand for?)
Molecular orbital theory (two things)
Planck and Einstein (almost at the same time)
de Broglie
Heisenberg
2. (10 pts) Using the Periodic
table, draw arrows showing the direction of increasing ionization energy.
In the space provided below, explain each arrow
using concepts from the quantum-mechanical atomic model. Be concise (terse).
3. (5 pts) What is the origin of paramagnetic
behavior in the elements?
4. (5 pts) Use quantum-mechanical atomic theory to
explain why Ca prefers to NOT exist as a +1 or +3 cation.
5. (15 pts) These is a very real controversy over
the storage of milk on the grocery shelve since electromagnetic radiation can
destroy the very important vitamin D that is added to it. The most likely bond to be broken is
one of the many carbon-hydrogen bonds present in vitamin D. After one of these bonds is broken the
molecule further decomposes and decreases the nutrition value of the milk. Calculate the wavelength of one mole of
photons that would be necessary to break a C-H bond. DH for a C-H bond is 414 kJ/mol.
6. (5 pts) Comparing Cl2,
Br2, and I2
Why is Cl2 as gas and I2 a
solid at room temperature and pressure?
7. (10 pts per compound) Draw Lewis dot structures for the two
compounds below and answer the following equations.
a) Sulfate ion (SO42-)
Draw the Lewis Dot Structure:
Draw all resonance structures and label each atom in
each structure with formal charges:
What is the hybridization of the central atom?
b) Ozone, O3
Draw the Lewis Dot Structure:
Draw all resonance structures and label each atom in
each structure with formal charges:
Draw the resonance hybrid for ozone.
What is the hybridization of the central atom?
8. (4 pts) The stratospheric ozone layer can be
destroyed by a number of chemicals.
One of these is methyl bromide (with a chemical bond energy of kJ/mol). Methyl iodide (with a bond energy of
kJ/mol) has been recently approved as a replacement with experiment data
suggesting that less CH3I will make it to the stratosphere for O3
destruction. Formulate a
hypothesis explaining the experimental observation based on your understanding
of Periodic trends and bond energies (and you should not need a Periodic table
or bond energies to solve this).
9. (3.3 pts each) in three
parts:
Draw the Lewis dot structure for a water molecule
and show the direction of the dipole.
What type of intramolecular
bond holes the water molecule together?
What type of intermolecular force (bonds) holds many
water molecules together in the liquid form?
Bonus:
(5 pts)
Draw the ÒHoly GrailÓ figure showing why human caused global
warming is real. What is the key
to understanding why global warming is human caused (point to this in your
graph)?