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Experiment to investigate the Chemical Composition of Minerals
Objective
In this experiment, you will react a variety of minerals with hydrochloric Acid to determine their
chemical composition.
Research Question
How does a sample’s reaction with Hydrochloric acid depend on the the chemical composition
of a mineral?
Thesis
If a mineral contains CO3 (is a carbonate) then it will react with HCl, forming CO2
gas.
Materials
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Electric Balance
Watch Glass
500 mL Beaker (±5 mL)
100 mL Graduated
Cylinder (±5 mL)
Gas Syringe
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3 samples of Calcium
Carbonate
3 samples of Dolomite
3 samples of Silicon
Dioxide
6 M HCl
Safety and Environmental Care
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1
Avoid any skin contact with HCl
Wear full coverage splash proof lab goggles to protect your eyes when
working with acids
Have adequate ventilation when working with hydrochloric acid\
Helen Scott
Candidate Number:
SL Chemistry
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Variables
Independent:
-Mineral used
-Molarity of HCl
Dependent:
-Amount of CO2 released
-Change in Mass
Method
1. Make sure all lab materials have been well cleaned.
2. Weigh the sample of Calcium Carbonate on the electric balance. Record data in the table.
3. Measure 100 mL of HCl into a 300 mL beaker.
4. Place the Calcium Carbonate sample into the acid.
5. Quickly cover the beaker with the Gas syringe apparatus, measuring how much CO2 is
released, record your findings in the data table.
5. Observe the reaction. Once it ends remove the mineral sample and once dry, weigh it again.
Record data in the table.
6. Repeat the procedure twice using a new sample of Calcium Carbonate and then with
Dolomite and Silicon Dioxide.
Setting Up
2
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Results
Using the data collected from the mass of the acid, and the initial and final masses of the
mineral sample, calculate the percent of sample lost to the reaction.
Disposal
Discard the mineral sample in the waste basket. Flush the acid down the sink with plenty of
water.
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Background Information
Reaction with Acids is a property of minerals that can help identify carbonate minerals. Dilute
hydrochloric acid will be used in this lab to react with a variety of minerals. The release of
appreciable bubbles of carbon dioxide in a relatively short period of time indicate that the
mineral being tested is a carbonate.
A carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, CO32.
The mineral samples used are:
Calcium Carbonate, CaCO3 (Limestone)
Dolomite, (CaMg)(CO3)2
Silicon Dioxide, SiO2 (Quartz)
The volume of gas formed can be calculated according to the equation:
𝛥𝑉 = 𝑉2 − 𝑉1
ΔV = Amount of gas formed
V1=the initial value you started with
V2=the amount left after the reaction
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Raw Data
Table 1.0 – Table to show raw data collected for all three food types
Initial Mass
Final Mass
Initial Gas
Final Gas
(±0.01 g)
(±0.01 g)
Volume
Volume
(±0.05 mL)
(±00.5 mL)
Calcium Carbonate
Trial 1
Trial 2
Trial 3
Dolomite
Trial 1
Trial 2
Trial 3
Silicon Dioxide
Trial 1
Trial 2
Trial 3
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Observations
Calcium Carbonate
Dolomite
Silicon Dioxide
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Processed Data
Table 2.0 – Table to show the amount of gas formed in each trial and the average change in
mass for each type of mineral.
Gas Formed
Average Volume of Gas Formed
(±0.05 mL)
(±0.05 mL)
Calcium Carbonate
Trial 1
Trial 2
Trial 3
Dolomite
Trial 1
Trial 2
Trial 3
Silicon Dioxide
Trial 1
Trial 2
Trial 3
Figure 2.1 – Example calculation of the volume of gas formed in the first trial of Calcium
Carbonate
𝛥𝑉 = 𝑉2 − 𝑉1
Uncertainty Calculation
=
The absolute uncertainties are added:
=
7
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SL Chemistry
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Table 3.0- Table to show the change in mass in each trial and the average change in mass for
each type of mineral.
Change in Mass
Average Change in Mass
(±0.02 g)
(±0.02 g)
Calcium Carbonate
Trial 1
Trial 2
Trial 3
Dolomite
Trial 1
Trial 2
Trial 3
Silicon Dioxide
Trial 1
Trial 2
Trial 3
Figure 3.1 – Example calculation of the change in mass of the first trial of Calcium Carbonate.
ΔMass = Final Mass – Initial Mass
=
=-
Uncertainty Calculation
The absolute uncertainties are
added:
=
=
8
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Figure 3.2 – Example calculation of the average change in mass of Calcium Carbonate.
MeanΔMass =
∑ 𝛥𝑀𝑎𝑠𝑠
Uncertainty Calculation
𝑛
When the average of a set of
values is taken, the uncertainty
remains the same:
=
=
±_
Table 4.0 – Table to show the correlation between volume of gas formed and change in mass
Average Change in Mass
Average Volume of Gas Formed
Calcium Carbonate
Dolomite
Silicon DiOxide
Figure 4.1- Graph to show the correlation between volume of gas formed and change in mass in
the reaction with Calcium Carbonate
9
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Figure 4.2 - Graph to show the correlation between volume of gas formed and change in mass
in the reaction with Dolomite
Figure 4.3 - Graph to show the correlation between volume of gas formed and change in mass
in the reaction with Silicon Dioxide
10
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Conclusion
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Helen Scott
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Evaluation
The effect of random errors would be reduced by the repetition of the trials for each mineral.
Factor
Gas lost to environment
Effect on Experiment
The measurement of gas formed
can be inaccurate because of
factors leading to the loss of gas
to the environment. Human
error, and an unsound piece of
equipment could contribute to a
slightly skewed result.
Incomplete reaction
between minerals and
acid
Since not the entire mineral is
CO3 the rock would not
completely dissolve, this would
mean that it would be virtually
impossible to accurately tell
when all of the CO3 has been
reacted with and dissolved. This
would lead to an incomplete
reaction and therefore slightly
skewed results.
Surface Area of
Minerals
The surface area of each
sample was different and the
Dolomite was powdered, this
difference would contribute to
results that were not wholly
comparable based on the
difference of surface area left to
react, which would change the
rate of reaction.
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Improvement
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Works Cited
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