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CCST105
Summer 2013 Final Exam
Name:
________________________
Final Exam
The Chemistry of CSI
(200 points)
You will only need a pen or a pencil and a calculator to finish this exam
You are encouraged to look over the entire exam
before beginning to write your answers
YOU MUST SHOW WORK FOR ALL CALCULATIONS
Problem
I A First Look at Forensic Chemistry (50 points)
II Chemical Reactivity and Molecular Shapes (50 points)
III Aqueous Chemistry (50 points)
IV Forensic Chemistry (60 points)
Total: (200 points)
Score
I A First Look at Forensic Chemistry
Consider the compound arsenic (III) oxide, (As2O3), which is typically used in
poisonings
a) What are the elements and how many of each are present in arsenic (III) oxide
b) What is the molecular weight of arsenic (III) oxide?
3. Write the electronic configuration for the element elements phosphorous and
magnesium
4. Write the answer to the following mathematical problems with the correct number of
significant figures:
40.99 +17.60 + 12.10 =
9.0 X 3.00 x 212 =
5. Chlorine is important to our everyday life. The element undergoes extensive reactions
in nature making both ionic and covalent compounds. (8 points)
a) What is the definition of an ionic compound and provide an example of an ionic
compound that contains chlorine.
b) What is the definition of a covalent compound and provide an example of a covalent
compound that contains chlorine.
6. Potassium chlorate KClO3 is used as an explosive in fireworks. Balance the following
chemical equation for the decomposition of potassium chlorate:
KClO3

O2
+
KCl
7. The Haber process is responsible for most of the ammonia (NH3) production in the
world :
N2 + 3H2  2NH3
If you have an excess of N2 and 8g of H2 in the reaction, how much ammonia would you
make (in grams)?
II Chemical Reactivity and Molecular Shapes
1. Provide the shape for the following molecules:
3. Name the following compounds:
NaCl
SiO2
N2O5
CoCl3
4. Give the chemical formulas of the following compounds:
vanadium(III) iodide
dichlorine heptoxide
carbon nitride
III. Aqueous Solutions
1. What is the range of the pH scale and what pH is basic?
2. Your blood is made up of a HCO3:CO2 buffer system. What does a buffer system do
and why is it important for your blood?
3. Europium chloride hexahydrate EuCl3. 6H2O is used to prepare a dye that used to
visualize fingerprints detected using fuming superglue. The solution is made by adding
1.00g of europium chloride in 800 mL. What is the molarity of the solution? Hint: the
water is part of the chemical formula and must be included in the weight.
4 If 10 mL of the solution in 2 is diluted to 950 mL, what is its new molarity?
5. Why is molecular shape important when considering the interactions of drugs and the
body?
6. Rank the following solutions in order of increasing boiling point. Explain your
reasoning
0.1 M (HN4)2SO4
0.2 M CuSO4
0.15 M KI
7 . Define osmosis and describe what happens to red blood cells if they are placed in a
hypertonic solution
IV Forensic Chemistry
1. Blood spatter can provide critical evidence in where things were during the
commission of a crime. How can blood spatter help determine what happened at a crime
scene?
Consider this sample blood drop from what direction did the blood originate? How
could you figure out the angle of impact?
2. Why is the size of the sample collected not as important when collecting a
homogeneous sample from a crime scene? Why are their guidelines for sample
collection in forensics?
3. It requires approximately 2700 accumulated degree hours (ADH) for a species of
blow fly to become 14 mm maggots. Assume that this species is the first to deposit eggs
on a body. Determine the time of death of a body discovered at 5 A.M. (with 14 mm
maggots) in an apartment with the thermostat set at 62oF.
4. How is forensic entomology used in determining the time of death? What factors
must be considered?
5. Explain, briefly, rigor mortis, algor mortis and livor mortis.
6. How does psychology play a role in solving crimes?
7. What is the percent of the general population that has a 12,12 pattern on TPOX and a
8,14 pattern on D16S539? How many people would you need to find this pattern?
8. Consider the DNA sequence [GACAAAAAC]. what amino acids does this sequence
code for? Hint go to the formula sheet, Find table 14.2 and use the fact every three letters
in the sequence code for an amino acid
9. Explain how an immunoassay works
10 Describe two other forensics techniques that we learned about this semester
BONUS: 8. (Difficult!) A body was discovered on January 3rd at 10:00 am . The average
temperature in the area was as follows Jan 3rd 50 oF Jan 2nd 65 oF Jan 1st 63 oF Dec 25th
–Dec 31st 55 oF. 14 mm maggots (3rd stage) of the blow fly were discovered on the body,
what is the approximate time of death? It takes 72 hours at 70 oF to reach the 14 mm
maggot stage.
Useful Formulas and Constants
Physical Constants:
Speed of light (vacuum)
c
3.00 X108 m/s
Plank’s constant
h
6.62 x 10-34 J·s
Mass of a proton
p
1.0073 amu
Mass of a neutron
n
1.0087 amu
Mass of an electron
e-
0.005486 amu
Equations:
c= 
E = h V1 = M2V2
Tfreezing = iKfm
pH = - log[H+]
Common Polyatomic Ions:
CN- Cyanide
SO42- Sulfate
NO3- Nitrate
Strong Acids
HCl Hydrochloric
H2SO4 Sulfuric
HNO3 Nitric
Conversion Factors:
1Mx =
1kx
=
1x
=
1mx =
1x =
x = s, g or m
1000 kx
1000 x
1000 mx
1000 x
1000 nx
Visible light colors and wavelengths:
violet
blue
green
380–450 nm
450–495 nm
495–570 nm
yellow
orange
red
570–590 nm
590–620 nm
620–750 nm
Tboiling = iKbm