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

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.   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.     

Toxic substance

Lethal dose (g of toxicant per kg of body mass)

Lethal dose for your victim

Lead 0.45 g/kg

Arsenic 0.075 g/kg

Mercury 0.2 g/kg

Chromium 0.25g/kg

______________________________________________________________________________ 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. Substance Mass

(g) % composition

Nitrogen

0.23

Carbon

0.45

Oxygen

0.67

Silicon

0.19

Lead

0.05

  Designed by Sara Adamek, modified for Willowbrook High School by Kira Bonk  

Location 1: Abandoned Mine Substance

Typical percent composition

Nitrogen 10-35

Carbon 8-18

Oxygen

31-39

Silicon

8-14

Lead

0-5

Location 2: The Toxic Waste Recycling Center Substance

Typical percent composition

Nitrogen 12-15

Carbon 20-30

Oxygen

40-49

Silicon

9-13

Lead

1-4

Location 3: MGB Manufacturing Plant Substance

Typical percent 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 Substance  (g)    Substance  mol            (g) 

Arsenic  

603    Arsenic  7.92   

Bromine  

45    Bromine  0.56   

Cadmium  

287    Cadmium  2.25   

Chromium  

23    Chromium  0.058   

Cobalt  

9063    Cobalt  153.79   

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  

  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.