Name _________________________
MURDER MYSTERY: Stoichiometry Edition
You are the lead investigator on the case of a murdered athlete. You must find out how the
victim was killed and who killed him, using your knowledge of stoichiometry. Read the
instructions, find the evidence, and solve the case.
________________________________________________________________
Victim information:
Case # 153
Name: Jasper Chan
Age: 24
Sex: M
Height: 5’10” Weight: 154 lbs
Information:
The victim is a minor league baseball player for the Kane County
Cougars. He lived alone in a one bedroom apartment 5 blocks
from the stadium. His teammates say he was a nice guy. He has
a mother and younger sister in Seattle, WA. This was his first
season with the Cougars. He played for the Quad Cities River
Bandits for two years before transferring to the Cougars in
December. When he wasn’t practicing or traveling with the team
he played a lot of Xbox.
______________________________________________________________________________
There was no sign of injury on the body so you suspect the victim was poisoned. You instruct
the lab to do a toxicology screen and look for poisons. When you get the toxicology report back
you find out that the lab tech forgot to convert the moles of toxic metals into grams. Luckily,
you paid attention in chemistry and remember how to do those conversions.
______________________________________________________________________________
Toxicology report for case # 153
There were traces of lead, arsenic, mercury, and chromium in the
blood. Very small amounts of these toxic metals will not kill a
healthy adult, but if the dose is high enough the individual
will die. The amounts of toxic substances found in the body are
listed below.
Substance
Amount in body (mol)
Amount in body (g)
Lead
1.21 x 10-3
Arsenic
0.0806
Mercury
0.023
Chromium
0.201
Designed by Sara Adamek, modified for Willowbrook High School by Kira Bonk
What a lethal dose is depends on the mass of the individual.
For example, if the individual massed 1 kg, a lethal dose of
lead would be 0.45 g. If the individual massed 20kg, a lethal
dose of lead would be 9 g. Remember: 1 kg = 2.20 lbs
Toxic
substance
Lead
Lethal dose
(g of
toxicant per
kg of body
mass)
0.45 g/kg
Arsenic
0.075 g/kg
Lethal dose
for your
victim
Was your victim poisoned? If so,
which substance killed him?
While you were waiting for the
toxicology report you went to
check out the victim’s apartment.
Chromium
0.25g/kg
At the apartment you noticed
muddy footprints on the balcony
and signs that the sliding glass door had been forced open. You suspect that the muddy prints
might come from the killer. After photographing the footprints you take a sample of the mud
to the lab for analysis. When you get the report back, you find out that the lab tech has been
lazy and did not convert the numbers to percent composition like you expected. But again,
you remember how to do this from your days in chemistry.
______________________________________________________________________________
Analysis of soil for case #153
The mud from the foot prints was analyzed and the results are
below. Nitrogen, carbon, oxygen and silicon are usually found
in soil samples. Lead is not. This suggests that the soil that
made the prints came from one of three locations in this area.
The profiles of the soils in these areas are below the findings.
Mercury
0.2 g/kg
Substance
Nitrogen
Mass
(g)
0.23
Carbon
0.45
Oxygen
0.67
Silicon
0.19
Lead
0.05
%
composition
Designed by Sara Adamek, modified for Willowbrook High School by Kira Bonk
Location 1: Abandoned Mine
Typical percent
Substance
composition
Nitrogen
10-35
Carbon
8-18
Oxygen
31-39
Silicon
8-14
Lead
0-5
Location 2:
Substance
Nitrogen
The Toxic Waste Recycling Center
Typical percent
composition
12-15
Carbon
20-30
Oxygen
40-49
Silicon
9-13
Lead
1-4
Location 3: MGB Manufacturing Plant
Typical percent
Substance
composition
Nitrogen
10-16
Carbon
23-35
Oxygen
30-41
Silicon
11-18
Lead
0-4
________________________________________________________________
Given the above information, which location do you think you should investigate?
Designed by Sara Adamek, modified for Willowbrook High School by Kira Bonk
You go to check out the toxic waste recycling center. It occurs to you that perhaps the killer got
the toxins from the center. When you speak to the manager you find out that two different
departments are in charge of keeping records. The intake department keeps the records in
terms of grams of a substance they receive; the processing department keeps their records in
moles. You decide to compare the number of grams of each substance in order to determine if
anything went missing. Once again your chemistry knowledge comes to the rescue!
______________________________________________________________________________
Intake Records
Processing Records
2/14-2/17
2/14-2/17
(g)
Substance
(g)
Substance
mol
Arsenic
603
Arsenic
7.92
Bromine
45
Bromine
0.56
Cadmium
287
Cadmium
2.25
Chromium
23
Chromium
0.058
153.79
Cobalt
9063
Cobalt
Lead
386
Lead
1.86
Mercury
745
Mercury
3.66
Molybdenum
22
Molybdenum
0.23
______________________________________________________________________________
Could the substance that poisoned your victim have come from the toxic waste recycling
center? How do you know?
Is anything else missing?
After reviewing the records from the recycling center, you decide you need to see the security
footage. The video from two weeks ago shows a person entering the facility late at night and
then leaving 20 minutes later carrying a large bag. Another video shows a truck leaving. You
run the truck’s license plate and find out it belongs to the manager of the Cougars. You go talk
to him and find out that he was out of town on a recruiting trip the night the truck made a trip
to the recycling center. You ask who has access to the truck and find out that all of the players
are allowed to borrow it if they need it. The keys are kept in the team locker room.
Designed by Sara Adamek, modified for Willowbrook High School by Kira Bonk
You pay a surprise visit to the locker room and discover several mysterious substances in one of
the player’s lockers. You rush the samples to the lab and eagerly await the results.
________________________________________________________________
Analysis of unknown substances for case #153
Substance #1 is As2O3. There was 0.020 mol of the substance.
Substance #2 is CrCl6. There was 0.19 mol of the substance.
Substance #3 is Hg3(PO4)3. There was 8.31 x 10-3 mol of the
substance.
________________________________________________________________
You know that if the masses of the As, Cr, and Hg from the samples match those of the missing
chemicals from the recycling center you will have enough evidence to arrest the teammate for
the murder of Jasper Chan. But how can you figure out if the masses match? You will have to
write balanced equations showing the decomposition of each of the substances into their
component elements and then use stoichiometry to covert from moles to grams.
Now that you are finished analyzing the evidence, summarize your findings for your Sergeant
and describe the next step you are going to take with the investigation. Make sure to logically
lay out your reasoning and site the evidence that you feel is relevant.
Designed by Sara Adamek, modified for Willowbrook High School by Kira Bonk