Determining the Chemical Formula of
Copper (II) Sulfate Hydrate
Your Name
Lab Partner(s): ________________
Date Performed: _______________
Date Submitted: _______________
Course: SCH3U1
Teacher: Mr. Khalid
Father Michael Goetz SS
Abstract:
The purpose of this investigation was to determine the mass percentage of water and the
chemical formula of the hydrate of copper (II) sulfate. In this investigation, a mass between 2.00g and
4.00g of copper (II) sulfate hydrate was weighed inside a beaker, and heated at a medium setting on
a hot plate until the blue coloured crystals became a white-grey colour, indicating that the water from
the hydrate had evaporated. After the colour change occurred, the mass of the anhydrous salt was
measured to be 1.45g and the mass of water evaporated was calculated to be 0.55g.
In conclusion, from the data collected the percentage of water in the hydrate was calculated to be
27.50%, and the chemical formula of the hydrate was determined to be CuSO4 ∙ 3H2O.
Introduction:
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Brief essay (maximum 250 words) about the history and theory behind the experiment
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For example, in an introduction to the Hydrate Lab you might discuss the following: What is a
hydrate? What are their properties? What are some examples of common hydrates? Are there
any historically interesting facts about the use/discovery of hydrates?
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Should include in-text citations linking to the references section, where appropriate. For
example:
“The development of new ionization techniques over the last century has played a pivotal role
in the development and refinement of modern mass spectroscopy (Smith et al., 2009).”
Hypothesis:
If the mass of water in the hydrate can be measured, then it will be possible to compare the amount
(in moles) of the anhydrous ionic compound to the amount of water. This ratio should reveal the
number of water molecules in the hydrate because all chemical compounds follow the Law of Definite
Proportions.
Materials and Set up:
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Goggles
Apron
1 glove
Glass stirring rod
Beaker tongs
Hot plate
Hot pad
Scoopula
Electronic centrigram balance
2.00g to 4.00g copper (II) sulfate
hydrate
Fig.1: Experimental apparatus used to determine the chemical
formula of a hydrate and the mass percentage of water.
Procedure:
Safety Considerations: According to the Material Safety Data Sheet for copper (II) sulfate, this
substance is a skin and eye irritant. Skin and/or eye contact must be followed with immediate flushing
with water. The substance should be handled with care and goggles must be worn. Proper disposal
measures must be taken – copper (II) sulfate cannot be disposed down the sink.
1. The mass of the empty beaker was measured on the electronic balance and recorded in the
table.
2. About 2.00 g to 4.00 g of hydrated copper (II) sulfate was added to the beaker (actual mass:
3.04 g). The total mass of the beaker with the hydrate was measured and recorded.
3. The beaker was placed on top of the hot plate and heated at a low-medium temperature
setting. The beaker was heated until the crystals lost their blue colour and took on a uniform
white-grey. The glass rod was used to stir the crystals occasionally.
4. Once the crystals lost their colour, the beaker tongs were used to place the beaker on the hot
pad to cool down.
5. The mass of the beaker with the white powder (anhydrous salt) was measured and recorded.
6. The anhydrous salt was disposed of, in the waste jar. The beaker was rinsed once with a small
amount of water which was also added to the waste jar. The beaker and glass rod were
thoroughly washed.
Results/Observations:
Table 1: Quantitative observations of the materials used in the experiment
Item(s)
Mass (g)
Empty beaker
172.47
Beaker with hydrated copper (II) sulfate
174.47
Hydrated copper (II) sulfate
2.00
Beaker with anhydrous copper (II) sulfate
173.92
Anhydrous copper (II) sulfate
1.45
Water evaporated
0.55
Table 2: Qualitative observations of materials in the experiment
Before
Beaker: Clear
Hydrated Copper (II) sulfate:
Solid blue crystals, odourless
During
-Beaker: became steamed up
-Blue crystals began to turn
white
After
-Beaker: clear
-Crystals have become whitegrey in colour, remain solid but
more powdery.
Discussion (analysis/calculations)
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Answers to all the analysis questions assigned in numerical order.
If the question has mathematical work, show all of your work including formulas, and provide
your answer to the correct number of significant digits.
If a calculation is repeated many times only show ONE example of the calculation in a section
with the heading “Calculations”, before the answers to your discussion questions.
Conclusion
In this experiment, the mass of the water in the hydrate was determined to be 0.55 g, which
yields a percentage 27.50% of water in the copper (II) sulfate hydrate. The chemical formula of the
hydrate was calculated to be CuSO4 ● 3 H2O, not CuSO4 ● 5 H20. Therefore, the hypothesis was not
supported by this evidence. This experiment yielded a percentage error of about 8.70%, making
these results quite reliable. Some sources or error that may have occurred in this experiment are;
instrumental shift of the electronic balance due to drafts, and the electronic balance used has a finite
precision, these errors would throw off all the mass results. Also, the hydrate may not have been
heated long enough therefore all the water may not have evaporated out, the hydrate may have been
heated too long and copper (II) oxide could have formed, and some of the anhydrous salt may have
still been stuck on the glass rod, all of which would result in errors when measuring the mass of the
anhydrous salt and therefore, result in errors when calculating the mass of water evaporated.
References
Haber, S., Salciccioli, K., & Sanader, M. (2011). Chemistry 11. Toronto: Nelson Education.
Ortega Arango, S. (2013, May 07). Canada drops out of race to tap methane hydrates. Retrieved
from http://www.cbc.ca/news/technology/canada-drops-out-of-race-to-tap-methane-hydrates1.1358966