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Hydrated Crystals
HASPI Medical Chemistry Lab Draft
Background/Introduction
Magnesiusm In The Body
Magnesium (Mg) is a mineral that is present in large amounts in the human body. It is a very
important cofactor in more than 300 chemical reactions that keep the body working properly,
including but not limited to:
 Protein synthesis
 Energy production
 Muscle contraction
 Structural development of bones
 Brain and nerve function
 DNA and RNA synthesis
 Blood glucose control
 Neutralizing stomach acid and
 Blood pressure regulation
peristalsis in the intestines
The average person’s body contains about 25 grams of magnesium, with 50-60% stored in the bones.
People get magnesium through their diet and levels are largely controlled by the kidneys. On
average, about 120mg of magnesium is excreted into urine each day.
Dietary Intake of Magnesium
Magnesium is widely distributed in plant
Table 1: Recommended Dietary Allowances for Magnesium
AGE
MALE
FEMALE
PREGNANCY
LACTATION
and animal foods and beverages. Nuts,
Birth – 6 months
30 mg
30 mg
seed, whole grains, and vegetables like
7-12
months
75 mg
75 mg
broccoli, squash, and spinach are good
1-3
years
80 mg
80 mg
sources of magnesium. In general, foods
4-8
years
130 mg 130 mg
that are high in fiber are high in
9-13
years
240 mg 240 mg
magnesium. Other sources include dairy
14-18
years
410 mg 360 mg
400 mg
360 mg
products, meats, chocolate, and coffee.
19-30 years
400 mg 310 mg
350 mg
310 mg
Sometimes magnesium supplements are
31-50 years
420 mg 320 mg
360 mg
320 mg
needed if magnesium levels are too low
51+ years
420 mg 320 mg
and are readily available in a variety of
forms. Table 1 outlines the Federal Drug
Administration’s Recommended Dietary Allowances for magnesium by age and gender.
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Magnesiusm and Health
Magnesium deficiency due to low dietary intake is uncommon but risks include habitually low intake
or excessive losses of magnesium due to certain health conditions, chronic alcoholism, and/or the use
of certain medications. Signs of magnesium deficiency can be as mild as a loss of appetite, nausea,
vomiting, and fatigue. In more severe cases individuals may experience numbness and tingling,
uncontrolled muscle contractions and cramps, seizures, personality changes, abnormal heart
rhythms, and hypocalcaemia or hypokalemia (low levels of calcium and potassium due to a
disruption in mineral homeostasis).
Research has shown that magnesium deficiencies might be involved in cardiovascular disease, type 2
diabetes, osteoporosis, and migraine headaches. While more well-designed, large trials are needed
for more evidence, some studies suggest that magnesium supplementation can cause a small decrease
in blood pressure among hypertension patients and reduce the risk of stroke. Likewise, diets with
higher amounts of magnesium are associated with significantly lower risks of diabetes, osteoporosis,
and chronic migraine headaches.
Too much magnesium is not a big health risk because properly functioning kidneys eliminate excess
amounts in urine. However, high doses of magnesium from dietary supplements or medication can
result in diarrhea and abdominal discomfort. Magnesium toxicity in the body usually only occurs
when individuals consume upwards of 5,000 mg/day, which is more than ten times the FDA’s
recommended daily allowance.
Magnesiusm in Medications and Treatments
Magnesium sulfate (MgSO4), also known as Epsom Salt, is one of many magnesium containing
compounds that can be used for medical treatment. Magnesium sulfate can be prescribed for many
reasons and can be bought at the local grocery store for a number of home remedies. If taken orally,
magnesium sulfate holds on to water in the large intestine, preventing the body from reabsorbing
fluids. This will cause the bowels to evacuate and can help someone who has constipation.
Magnesium also depresses the central nervous system, blocking nerve signals in the muscle. Soaking
in a bathtub of warm water and Epsom Salt can help alleviate body aches and pains. If prescribed by
a doctor, other magnesium containing compounds can help stop seizures by limiting muscle
movements.
Magnesium can also be used for treating attention deficit-hyperactivity disorder (ADHD, anxiety,
chronic fatigue, Lyme disease, fibromyalgia, and if applied topically it can be used to treat infected
skin ulcers and speed up wound healing.
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Review Questions
1.
2.
3.
4.
5.
What role(s) does magnesium play in the human body?
How does the body regulate magnesium levels?
What types of foods are good sources of magnesium?
What is your recommended daily intake of magnesium according to the FDA?
Why do you think the recommended daily allowance of magnesium increases for pregnant
females?
6. Is it possible to have too little/too much magnesium in your body? What happens if that
happens?
7. Give an example of a magnesium containing compound and explain how it can be used
for medical purposes.
Hyrdrated Crystals
HASPI Medical Chemistry Lab # A
Scenario
A water molecule has a strong dipole, which means it has partial
charges on either end. This is due to the asymmetric structure of
water and the uneven electronegativity between hydrogen and
water. Because of these partial charges, water is very attracted to
ions.
Figure 1: The polarity of water
This attraction is the reason that ionic substances dissolve and dissociate in water. The water
surrounds the ions so that it can move around in the solution. In some cases, the water and
the ions are so strongly attracted that when the water is evaporated from the solution some of
the water molecules are trapped within the crystals that form. This happens in specific ratios
for the chemicals that form hydrates.
In this lab we are going to work with Magnesium Sulfate Hydrate, a crystal
made of MgSO4 and water. Your goal is to find the number of water
molecules for each magnesium sulfate in the system.
Figure 2: MgSO4
Removing water from the system requires energy, which makes the removal
of water an endothermic reaction. For many hydrates you can merely heat them for a period
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of time in order to force out the water. Once you have removed the water we call these an
anhydrate, a term used for the compound once the water is removed. This also means that if
you add water it is an exothermic process, where the energy is released as water is reintegrated into the crystalline structure.
Materials
Safety Goggles
Bunsen Burner
Ring Stand
Clay Triangle
Forceps
Crucible
Digital Scale
Procedure/Directions
Your lab team will be giving tasks, or directions, to perform on the left. Record your questions,
observations, or required response to each task on the right.
Task
Response
Obtain the necessary materials provided by your instructor.
1
Set up your Bunsen burner, stand, and clay triangle.
Be sure to keep your work area neat and organized. Wear safety goggles at all times at your work
station and secure all long hair and loose clothing.
2
Find the mass of your crucible and cover. Record
your measurement.
Mass of crucible & cover:
___________________g
3
4
Find the mass of your crucible, cover, and
magnesium sulfate sample. Record your
measurement.
Mass of crucible, cover & sample:
Using your measurement in step 2, calculate the
mass of just your magnesium sulfate hydrate
sample.
Mass of hydrate sample:
Carefully place your crucible, cover and sample
on the clay triangle and heat over a Bunsen
Hydrated Crystals, HASPI Medical Chemistry Lab DRAFT
___________________g
___________________g
Heat Start Time: ______________________
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burner for 10 minutes. Mark the time you start the
heating process and calculate the time you need
to remove your sample from the heat.
Date:
Heat End Time: _______________________
While heating your sample, you may work on
another assignment given to you by your
instructor. Be mindful of you Bunsen burner and
work area.
5
Turn off your Bunsen burner and let your crucible,
cover, and sample cool down for 20 minutes. Mark
the time you turned off the Bunsen burner and the
time it is safe to handle the crucible.
Cooling Start Time: ____________________
Cooling End Time: ____________________
While cooling your sample, you may work on
another assignment given to you by your
instructor. Be mindful of you Bunsen burner and
work area.
6
Once your crucible is cool enough to handle, find
the mass of the crucible, cover and heated
sample. Record your measurement.
Mass of crucible, cover & heated sample:
Since you already know the mass of crucible and
cover (step 2), calculate the mass of the heated,
anhydrous sample.
Mass of crucible & cover:
___________________g
___________________g
Mass of anhydrous sample:
___________________g
7
Using the data you gathered in step 3 and step 6,
calculate the amount of H2O in your sample.
Remember to use the correct number of
significant figures.
Mass of hydrate sample (Step 3):
___________________g
Mass of anhydrous sample (Step 6):
___________________g
Mass of H2O:
___________________g
8
Calculate the moles of H2O present in your
original MgSO4•XH2O hydrate sample.
Remember to use the correct number of
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significant figures.
9
Calculate the moles of anhydrous MgSO4 present
in your sample.
Remember to use the correct number of
significant figures.
10 Derive an empirical formula (ratio between H2O
and anhydrous MgSO4) for your original hydrated
sample. Use the moles calculated in steps 8 and
9. This ratio becomes the coefficients in your
compound.
____MgSO4•____H2O
11 Calculate the percent of water in a perfect sample
of magnesium sulfate. Use the formula:
MgSO4 • 7H2O
12 Calculate the percent of water in the magnesium
sulfate sample from your lab results. Use the
formula you calculated in step 10 based on your
mole ratio)
13 Calculate your percent of error based on results of
steps 11 and 12. Use your final% answers and
plug in to % error formula
𝐴𝑐𝑡𝑢𝑎𝑙 − 𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙
× 100
𝐴𝑐𝑡𝑢𝑎𝑙
Analysis & Interpretation
Summarize your data into the following data table:
Measurements
Magnesium Sulfate
Crucible, cover & sample
g
Crucible and cover
g
Hydrated sample
g
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Crucible, cover & heated sample
g
Crucible and cover
g
Anhydrous sample
g
H20 in sample
g
Moles of H20 in sample
mol
Moles of anhydrous sample
mol
Empirical Formula
Hydrated Crystals, HASPI Medical Chemistry Lab DRAFT
____MgSO4 • ____ H2O
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Analysis Questions
1. Explain why water is highly attracted to ions.
2. In this lab, you turned Magnesium Sulfate Hydrate into an anhydrous compound. Is
this an exothermic or endothermic reaction? Explain your answer.
3. The method used in this experiment to find the percentage of water in the hydrated
crystals is not suitable for all hydrates. Give at least two reasons why this may be
so.
4. Why should the mass of the crucible be measured immediately after the crucible
cools and not later?
5. Discuss 2 possible reasons for your observed percent error.
6. Your lab procedures were reproduced for a different hydrate sample, Copper II
Sulfate, CuSO4 • H2O. If the following values were taken before and after the
sample was heated, fill in the remainder of the data table to find the amount (in
moles) of H2O and Copper II Sulfate in in your sample.
Measurements
Copper II Sulfate
Crucible, cover & sample
39.47 g
Crucible and cover
35.44 g
Hydrated sample
g
Crucible, cover & heated sample
37.84 g
Crucible and cover
35.44 g
Anhydrous sample
g
H20 in sample
g
Moles of H20 in sample
mol
Moles of anhydrous sample
mol
Empirical Formula
Hydrated Crystals, HASPI Medical Chemistry Lab DRAFT
____CuSO4 • ____ H2O
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Connections & Applications
As per NGSS/CCSS incorporate extensions that allow teachers/students to choose outside activities
recommended by the standards.
Goal of having a minimum of 3 options for every lab activity, but more can be included. May include:
 Critical thinking question(s) requiring research
 Medical case study related and/or reinforcing concept
 Investigating a phenomena
 Designing an experiment
 Developing and/or building a model
 Creating a multimedia or visual display to convey a concept
 Conduct a research project (correctly citing text is crucial)
 Constructing an oral or written presentation/argument (correctly citing text is crucial)
 Collecting data and construction graphical representations
 Assess accuracy and credibility of a scientific publication
 Mathematical computations
Resources and References
List of references
 http://consideringyou.com/consider-this/all-about-magnesium/
 http://www.webmd.com/vitamins-supplements/ingredientmono-998MAGNESIUM.aspx?activeIngredientId=998&activeIngredientName=MAGNESIUM
 http://en.wikipedia.org/wiki/Magnesium
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