Molarity Murder Lab
Name:__________
Background Information: Simple solutions are composed of just two components. The solute is the component
in the lesser amount and is dissolved (like the kool aid powder in a glass of kool aid). The solvent is the component
present in the greater amount and is what dissolved the solute (like the water in a glass of kool-aid).
There are numerous methods of separating the components of a solution. The addition of heat will vaporize the
solvent, leaving the solute as a solid residue. Weighing the amount of solute residue will enable you to
complete calculations to determine if your solution sample fit the lethal dose.
From the coroner’s report: Ms. Scarlet is a 70 year old female, weighing 110 lbs. She has had long term
hypertension (high blood pressure) and is a Type 2 diabetic. According to the paramedics she was conscious
when they arrived with a rhythmic but rapid heartbeat. She was transferred for treatment at the local hospital.
During her first hours, she was hypertensive (high blood pressure 170/90mmHg), tachycardic (heart rate
120-130/min) and then hypotensive (low blood pressure 80/65 mmHg). Her state of consciousness changed
from somnolent (sleepy) to comma. The level of sodium chloride ions in her blood stream was extremely high.
Although she was given hypotonic infusions (more water) to correct hypernatremia (lack of water), the lethal
outcome occurred 15 hours after she had been hospitalized. On the basis of the clinical and post-mortem
findings, it was concluded that death was a direct consequence of excessive common salt intake.
Prior to her death, Ms. Scarlett was the judge of a Top Chef Contest. The latest challenge was for the
contestants to create a “meal fit for a queen” with an accompanying drink. Each contestant/suspect was found
with a colored drink they had prepared as part of their entry.
Your task: As part of the forensic team you will test drink samples for levels of sodium chloride, determine
which is the lethal sample, and determine the identity of the killer.
Sample A: Red
sample calculations
Sample B: Clear
Mrs. White
Sample C: Blue
Mrs. Peacock
Sample D: Purple
Professor Plum
Sample E: Yellow
Colonel Mustard
Sample F: Green
Mr. Green
Equipment:boiling flask, balance, pipette, 10 mL graduated cylinder, Bunsen burner, ring stand with ring,
clay triangle, tongs, striker
Procedure:
1. Weigh the clay triangle AND the empty boiling flask
2. Pour 10 mL of your solution into the boiling flask.
3. Position the ring, the clay triangle, and the boiling flask to be above the bunsen burner.
4. Use the striker to light the bunsen burner. Adjust the flame to get a 1-2 inch blue flame.
5. Let it boil the water away.
6. When the water is done, immediately turn off the bunsen burner.
7. Allow the evaporating dish to cool for 5 minutes. Work on your DLQ while you wait.
8. Weigh the clay triangle AND the boiling flask with the salt deposits.
WORK EXAMPLES !!!!
SAMPLE!!! Data from the experiment for solution A
A.
BEFORE BOILING! Mass of the clay triangle and empty boiling flask
83.120 grams
B.
AFTER BOILING! Mass of the clay triangle, boiling flask and salt crystals.
83.266 grams
C
Find the mass of the salt crystals.
Subtract! B - A = 0.146 g
EXAMPLE!!! Steps to calculate the grams of salt dissolved in the 250 mL drink.
1.
Use the mass of the salt in the flask.
1 mole of NaCl
~0.146 g
of salt
58.44 grams NaCl
= 0.0025
moles of salt
2.
Use the moles of NaCl from 1.
Calculate Molarity of solution. M = moles ÷ Liters
0.0020 moles NaCl ÷ 0.01 L = 0.25 M solution
3.
Use the M of solution from 2.
Convert 250 mL to Liters.
Calculate moles of sodium chloride in 250 mL drink
Mol = M x V
= 0.25 M x 0.25 L
= 0.0625 moles of NaCl in the 250 mL drink.
4.
Use the moles of chloride from 3.
Calculate the grams of NaCl in the 250 mL drink
0.0625
moles
NaCl
58.44 grams NaCl
1 mole of NaCl
= 3.65 g NaCl
in 250 mL
drink
EXAMPLE!!! Steps to determine if the grams of dissolved salt is lethal.
5.
Convert Ms.Scarlett’s body mass to kilograms
110
pounds
6.
Use Ms. Scarlett’s body mass in kg from 5.
How many grams would be lethal for Ms.Scarlet?
1 kilogram
2.205 pounds
49.9 kg
0.4 grams
1 kilogram
= 49.9
kilograms
= 19.96 g
lethal dose!!!
19.96 g of salt is lethal for a person who weighs 49.9 kg.
7
Was your sample above the lethal dose?
NO – 3.65 g is not over the lethal dose.
YOUR WORK!!!
Record your drink sample letter. Data from the experiment for solution ____.
A.
BEFORE BOILING! Mass of the clay triangle and empty boiling flask
B.
AFTER BOILING! Mass of the clay triangle, boiling flask and salt crystals.
C
Find the mass of the salt crystals.
Subtract! B - A = ________
EXAMPLE!!! Steps to calculate the grams of salt dissolved in the 250 mL drink.
1.
Use the mass of the salt in the flask.
=
2.
Use the moles of NaCl from 1.
Calculate Molarity of solution
3.
Use the M of solution from 2.
Convert 250 mL to Liters.
Calculate moles of sodium chloride in 250 mL drink
4.
Use the moles of chloride from 3.
Calculate the grams of NaCl in the 250 mL drink
Mol = M x V
EXAMPLE!!! Steps to determine if the grams of dissolved salt is lethal.
5.
Convert Ms.Scarlett’s body mass to kilograms
6.
Use Ms. Scarlett’s body mass in kg from 5.
How many grams would be lethal for Ms.Scarlet?
7
=
Was your sample above the lethal dose?
Is the creator of your drink sample guilty of poisoning Ms Scarlett?
Claim: Answer the question in a complete sentence.___________________________
_____________________________________________________________________
Evidence: Use your calculations as evidence to prove your claim is correct.
_____________________________________________________________________
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