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Determination of an Unknown Carbonate
from Carbon Dioxide Gas Evolved |
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Introduction In this experiment we will treat a
carbonate with an acid. In this case
we will use hydrochloric acid. Most of
you are probably familiar with this type of reaction since the reaction of
baking soda (sodium hydrogen carbonate) and vinegar (acetic acid) produces
carbon dioxide gas, sodium chloride and water. We will use a gas collection apparatus to
collect the gas and quantify the reaction.
The advantage of using this reaction is that we can quantify one of
the reactants, ie. the carbonate
and then separate one of the products, the carbon dioxide, from the reactants
and the other products. You will be
given two different divalent carbonates with which to work. Purpose: The purpose of this experiment is to
measure as accurately as possible the carbon dioxide produced when the
unknown carbonate is reacted with excess hydrochloric acid and then use this
information to identift the unknown divalent
carbonates (substance A & B) Hypothesis: You will need to predict what the
relationship what effect a change in volume or temperature will have on the
pressure of a gas. Background: . Include a paragraph or two on the use
of carbonates. |
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Materials
& Methods Materials: Unknown carbonate and 2M hydrochloric
acid Equipment: Pneumatic trough 125
mL flask or 25 x 200 mm Thermometer 600 mL
beaker One hole rubber stopper Rubber/plastic tubing 250 mL
graduate cylinder Safety: 2M hydrochloric acid is considered
concentrated acid. Goggles should be
worn and if acid comes in contact with eyes the eys
should be flushed immediately with water.
If acid comes in contact with skin or clothing the affected areas
should be rinsed thoroughly. Pre-Lab Procedure 1. Examine
the lab procedure and prepare a flow chart for how you expect to conduct the
exercise. 2. Familiarize
yourself with the gas laws. Procedure: 1. Set up the
gas collection apparatus as described by your instructor. 2. Perform
the gas collection sufficient number of times to ensure reproducible and as accurate results as possible. |
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Results & Conclusion Results: Prepare a table of your data. Show your calculation and be sure to
correct for the partial pressure of water vapor. Clearly state your identification of the
unknown metals Discussion/Conclusions: In your discussion/conclusion section
of your report discuss specifically how the results especially how
reproducible your data is and its implication for the correct identification
of the unknowns. Be sure to discuss
potential sources of error in your experiment and how the experiment might be
improved or modified to obtain better results. |
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Questions 1. What other
gases are present in the graduated cylinder.
Will they affect the over all result? 2. A 27.7 mL sample of carbon dioxide is collected over water at
25.0°C and 780 torr? What is the pressure due to the carbon
dioxide? 3. Describe
as means by which a gas could be collected without having to adjust for the
water vapor involved in collecting gas over water. 4. What
device specifically uses the reaction of baking soda with an acid? 5. Describe a
process that you could use to estimate absolute zero? |
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