DeterminingWhichZincCompoundWillResultinLargestBrassYieldWhenUsedtoPlateCopper.doc

CREATION OF BRASS THROUGH ZINC PLATING OF COPPER
IB Candidate Number: 002904-0104
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Determining Which Zinc Sample Will Result in Largest
Brass Yield When Used to Plate Copper
Alex Kaunzinger
Biotechnology High School
May, 2015 Exam Session
Extended Essay: Chemistry
Instructor: Lauren Ruthrauff
Word Count: 3923

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I. TABLE OF CONTENTS
a. Cover……………………………………………page 1
b. Table of Contents……………………………….page 2
c. Abstract…………………………………………page 3
d. Introduction……………………………………..page 4 - 6
e. Materials………………………………………...page 6 - 7
f. Methods…………………………………………page 7 - 8
g. Results…………………………………………..page 8 - 13
h. Conclusion………………………………………page 14 - 17
i. Literature Cited………………………………….page 18
j. Appendix…………………………………………page 19 - 20

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II. ABSTRACT
Brass, an alloy of copper and zinc, is an important strategic metal for various industrial
and commercial ventures; however the quantities that are needed in the United States for these
purposes are not manufactured within its borders. Much of the brass that is used in the United
States must be imported, increasing the nation’s dependence upon foreign entities in order to
obtain the necessary quantities to support the United States’ economy. A nation is at its most
stable point when it does not have to rely on the exports of other nations, therefore, if the United
States can limit its dependence upon other nations for their exports of brass, then this would be
beneficial for the stability of the nation. In order for the United States to limit their need for
brass, the answer is to create more brass. Therefore, the objective of this investigation is to
determine the optimal chemical samples for the creation of brass. This was determined through
the plating of several zinc samples onto pieces of copper with the application of a thermoplating
process that will result in the creation of a brass alloy. The samples that were tested were Zinc
acetate, Zinc sulfate, zinc dust, and zinc strips, along with a negative control of no zinc. The
initial hypothesis was that the zinc strips would result in the most brass alloy, however this
turned out to be not the case. The zinc dust was the most effective, followed by Zinc acetate,
Zinc sulfate, zinc strips, and the no zinc control. This means that the zinc dust should be used in
industry and commercial venues in order to increase the yield of brass, therefore decreasing the
United States’ dependency upon foreign entities.

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III. INTRODUCTION
Research Question: What is the optimal zinc sample for plating copper with zinc to create a
brass alloy?
The purpose of this experiment was to determine which zinc sample would result in the
largest brass yield when used to plate copper. In order to fulfill this purpose, mixtures of zinc
acetate, zinc sulfate, zinc powder, zinc strips, and no zinc were chosen to determine the
optimal zinc sample to be used in the creation of brass. These samples were used to plate
copper using a thermoplating technique where heat was applied to the mixture containing the
zinc sample and the copper. The amount of brass created was determined by using a 3:2 ratio
of zinc to copper.
As the 24th most abundant element on earth, Zinc (Zn) is a transition element found in the
outer transition section of the periodic table (Stevens 2012). It is a group 12 element,
meaning that, like other group 12 elements such as cadmium (Cd) and mercury (Hg), it is a
silvery-white metal with low boiling and melting points. (Britannica-Zinc 2013). Zinc’s
electron configuration is 1s22s22p63s23p64s23d10, so as with all group 12 metals, zinc has a
full d-sublevel with 10 electrons as well as having two valence elections, causing it to ionize
into a 2+ cation. Zinc’s major uses are in preventing corrosions in other metals such as steel,
iron, and copper through plating as it covers the metal with a coating that prevents the
corrosion of the metal (Stevens 2012). When plating with zinc onto other metals, such as

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copper, it will form alloys, which are mixtures of two or more metals. It is a fairly reactive
metal and often combines with nonmetals and metals to produce ionic compounds and alloys.
Copper (Cu) is also a transition element found in the outer transition section of the
periodic table. It is in group 11, meaning that, like the other elements of group 11 such as
Gold (Au) and Silver (Ag), copper is a very soft metal and has a very low resistance, causing
it to be extremely conductive for electricity and heat. It is resistant to corrosion and is not
very reactive to other elements. In addition to sharing chemical properties, it has a similar
coloring to gold. (Brittanica-Copper 2013). Copper’s electron configuration is
1s22s22p63s23p64s13d10 which is interesting because following the normal pattern governing
electron configuration, it would be 1s22s22p63s23p64s23d9. However, the copper atom
becomes much more stable when the 3d sublevel is fully filled, therefore an election from the
4s sublevel moves to the 3d sublevel, so the configuration becomes 1s22s22p63s23p64s13d10.
(McClure 2009) Copper can form into two ions, a 1+ cation (cuprous)
(1s22s22p63s23p64s03d10) or a 2+ cation (cupric) (1s22s22p63s23p64s03d9) depending on how
many electrons it loses. Copper, when plated with zinc, can be formed into the alloy, brass,
which is an important metal for its anti-corrosion properties and high conductivity.
Brass (Cu3Zn2) is an important strategic metal in the commercial and industrial areas of
nations across the world, especially the United States. With resources diminishing at a rapid
rate, the United States is being forced again and again to deal with unstable countries that are
rich in strategic metals and minerals, resources such as brass. If more brass could be created
with the plating of zinc onto copper, then the United States’ reliance on foreign powers for
brass would be reduced. Therefore, in the interests of striving for economic, industrial, and

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commercial self-sufficiency, methods for increasing the yield of this plating should be
investigated.
So then, if brass is an important metal and it can be obtained by plating copper with zinc,
then how can more brass be made? The methods used different zinc samples to create
varying amounts of brass. The results indicated the optimal zinc sample to be used in the
making of brass.
Thermoplating is the use of heat to change the atoms into ions. The heat energy excites
the electrons within the atoms of the materials that are being heated and causes the
transformation of the heat energy into chemical energy. This chemical energy is the
ionization energy that exceeds the amount of energy needed to cause the ionization of the
copper and the zinc by way of the reduction of zinc with zinc as a reducing agent. Copper is
just the final acceptor of the zinc. The zinc is reduced by the zinc itself, meaning that zinc is
its own reducing agent (Szczeoankiewicz 1995).
The investigation will assess the effectiveness of different samples of zinc in order to
determine the most effective one, or the sample that will produce the most brass. The
samples being investigated are: Zinc sulfate (ZnSO4 (s)), Zinc acetate [Zn (C2H3O2)2 (s)],
Zinc (Zn (s)), and Zinc dust (Zn (s)). Now it would stand to reason that the sample containing
the most concentrated amounts of Zinc would be the one to produce the most yield, and it is
for that reason that the hypothesis of this investigation is that Zinc strips will be the sample
with the highest yield of brass, as flat pieces can be placed directly over and under the copper
for supposed maximum exposure.

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IV. MATERIALS
The materials used for this experiment were: 1.0M NaOH (250 ml), deionized water
(dH20) (250 ml), beakers (5), 500 mL bottle used for storing NaOH, 500 ml graduated
cylinder, copper strips (25), hot plate, Zinc sulfate (ZnSO4 (s)) (75 g), Zinc acetate
[Zn(C2H3O2)2 (s)] (75 g), Zinc (Zn (s)) (75 g), Zinc dust (Zn (s)) (75 g), tabletop balance
(accurate to 0.001 g), Bunsen burner, magnetic stirrer, magnet retriever, glass stirring rod,
forceps, lighter, and weigh boats.
V. METHODS
This experiment’s independent variable was the type of zinc sample that was used. The
dependent variable was the zinc that was plated onto the copper, and subsequently, the
amount of brass that was created. The constants in this experiment were the amount of solute
in each trial, the amount of mixture in each trial, the temperature that the mixture was kept at,
and the speed of the magnetic stirrer during the making of the mixtures. Other constants
included the amount of time that the copper was placed in mixture, the height and
temperature of the Bunsen burner flame, the amount of time placed in the Bunsen burner, and
the accuracy of the balance. The procedure was conducted five times per variable, making it
so that 25 total trials were done.
The process used in determining the optimal zinc sample to be plated onto copper to
produce the highest yield of brass is called thermoplating, or heat plating in which the copper
is placed into a heated mixture with zinc. The heat causes the zinc to plate onto the copper
and when the copper is removed, it is heated again to form brass. This experiment was

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conducted in three phases: the creation of the mixtures, the plating procedure, and the final
transformation of zinc plated copper into brass.
Phase I of the experiment was the creation of the various mixtures involved in the
experiment. The first mixture was 0.5M NaOH (l), which provided a solvent for which the
zinc samples would dissolve into. The 0.5M NaOH (l) mixture was obtained by diluting 250
ml of stock liquid 1.0M NaOH (l) with 250mL of deionized water. The Zinc acetate mixture
was obtained by placing 75 g of solid Zinc acetate in 100 ml of the 0.5M NaOH (l) mixture.
A magnetic stirrer was then placed in the mixture and spun at 600 rpm while being heated to
100oC. This process was followed for each sample, with 75 g of solid Zinc sulfate in the
solid Zinc sulfate mixture, 75 g zinc dust in the solid zinc dust mixture, and 75 g of solid zinc
strips in the zinc strip trial. There was 0 g of zinc in the negative control trial. After the solute
was dissolved into the mixture, the magnetic stirrer was removed.
Phase II of the experiment was the plating portion of the procedure. This was the same
for all of the variables. The initial mass of a square piece of solid copper was measured and
then the copper was placed into the zinc mixture for a period of 20 minutes. During these 20
minutes, the mixture was kept at 100oC. After the 20 minutes had elapsed, the now zinc-
plated copper was removed from the mixture and rinsed to remove any residue that may be
present. At this point, the zinc-plated copper moved to phase III.
Phase III of the experiment was the creation of brass. The zinc-plated copper was held
over a lit Bunsen burner for a period of 3 seconds and the removed. It was during this time
that the brass was formed. The final mass of the brass was then measured and the change in
mass was calculated, which would be equal to the amount of zinc plated onto the copper. The

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values for each sample were then converted into the amount of brass created by way of mass-
mass stoichiometry. The means for each sample were calculated and used to determine the
standard deviation of the data sets. The means then underwent a T-Test to determine if they
were significantly different from the negative control.
VI. RESULTS
The results of this experiment were first examined qualitatively and then quantitatively.
As denoted by the figures later in this section, one can determined to a certain extent which
trials were more effective by looking only at the qualitative data, however the quantitative
serves to determine how much more effective the samples are from each other. The figures
below show the qualitative data, in order from most effective to least effective.
Plain solid copper that the zinc is to be plated on
Figure 1: Copper
can be seen in Figure 1. This is an almost identical image
to Figure 6, making it appear that zinc strips are the least
effective sample.
The result of the use of solid zinc dust to plate the
copper can be seen in Figure 1. There is a noticeably
bright area, denoted by the red box. This area is where
there is an especially high concentration of brass. This Figure 2: Zinc Dust
sample can be considered the most effective because it
has the most brass-like color. The browner edges show
that some of the zinc was not plated successfully onto

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the copper and did not make brass.
The result of the use of solid Zinc acetate to plate Figure 3: Zinc acetate the
copper can be seen in Figure 3. Again, there is a noticeably
brighter area. However, this one is much smaller with much
more non-plated copper around the edges.
The use of solid zinc sulfate to plate the copper can Figure 4: Zinc sulfate
be seen in Figure 4. There are still noticeable bright spots
present, however, they appear in isolated patches as shown
by the red circles. It is clear that the brown-colored copper
is the dominant color in this image.
The use of solid zinc strips to plate the Copper can be
Figure 5: Zinc strips
seen in Figure 5. Unlike the other figures thus far, there is no
clearly-defined area of brass present. In this figure there is a
very faint brass sheen to the entire piece of metal, making the
metal mostly copper with a light dusting of brass.

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The use of no zinc to plate the copper can be seen in
Figure 6: No zinc
Figure 6. There is clearly no brass present and the trial looks
Almost identical to Figure 1, which is regular untreated
copper. Since there is no zinc, there can be no reaction and
Therefore there can be no brass created.
Table 1: Calculated change in mass for each sample.
Change in Mass (+/- 0.002 g)
Trial Number Zinc acetate Zinc dust Zinc sulfate Zinc strips No zinc
1 0.104 0.213 0.081 0.056 0.002
2 0.106 0.216 0.086 0.061 0.002
3 0.099 0.205 0.084 0.059 0.001
4 0.101 0.212 0.087 0.057 0.001
5 0.105 0.204 0.088 0.057 0.001
The values in this table represent the change in mass from the initial copper square to the
final mass of the brass. This value was used to calculate the amount of brass that was created in
each trial. This was done using mass-mass stoichiometry. Stoichiometry is the mathematical

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conversion of an amount of one substance to an amount of another substance. It is done by
converting the mass of the substance given (the zinc), dividing it by the molar mass (65.41
g/mol) to convert it into the moles, multiplying that product by the molar ratio of the initial
substance to the next substance. The molar ratio is obtained from the balanced equation of the
reaction, shown below:
3Cu+ 2Zn Cu3Zn2
This means that for every one brass atom, two zinc atoms and three copper atoms are
required, causing the molar ratio of the brass to the zinc to be 1/2. The product of that is then
multiplied by the molar mass of the second chemical (brass = 321. 47 g/mol). Finally, the
mass of the brass was obtained, shown here.
Calculation of mass of brass
Mass of Zinc (change in mass) x 1 mol Zn/65.41 g x 1 mol Cu3Zn2/ 2 mol Zn x 321.47 g/
1 mol Cu3Zn2 = Mass of Brass
0.104 +/- 0.002 g x 1 mol Zn/65.41 g x 1 mol Cu3Zn2/ 2 mol Zn x 321.47 g/ 1 mol
Cu3Zn2 = 0.255+/- 0.002 g
Table 2: Calculated masses of brass
Mass of Brass (+/- 0.002 g)
Trial Number Zinc acetate Zinc dust Zinc sulfate Zinc strips No zinc
1 0.255 0.523 0.199 0.138 0.005
2 0.260 0.531 0.211 0.150 0.005
3 0.243 0.503 0.206 0.138 0.002

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4 0.248 0.521 0.213 0.140 0.002
5 0.258 0.501 0.216 0.140 0.002
These calculated masses of the brass were then used to calculate the mean for each
sample. Those values then were used to calculate the standard deviation to check for
consistency and precision during the experiment.
Table 3: Means of mass of brass for each sample
Sample Mean (+/- 0.010 g) with Standard Deviation
Zinc acetate 0.253 +/- 0.007
Zinc dust 0.514 +/- 0.013
Zinc sulfate 0.209 +/- 0.007
Zinc strips 0.141 +/- 0.005
No zinc 0.003 +/- 0.002
As one can see from just looking at the means, zinc dust appears to be the most effective
sample, followed by Zinc acetate, Zinc sulfate, Zinc strips and no Zinc. In order to be certain
of this trend, the means were placed in a bar graph to visually show the trend of
effectiveness. All the values of each sample underwent a T-test in order to obtain the p-
values for each sample. The p-values were determined by comparing each sample’s values to
the negative control. The null hypothesis was that the samples would not be significantly
different, however this was found to be unsupported as all the p-values were < 0.005,
therefore all the values were significantly different from the negative control.

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Graph 1: Effectiveness of Zinc samples in the creation of brass.
VII. CONCLUSION

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The results of this experiment described the effectiveness of each of the zinc samples
used to plate copper in order to create brass. The results of this experiment indicated that it
was zinc dust that was by far the optimal sample to be used in the plating of zinc onto copper
with a mean mass of brass created of 0.514 +/- 0.010 g. The results also indicated that the
other samples were less effective than the zinc dust, which is supported by the means of the
brass created by each of the samples. In order of decreasing effectiveness, zinc acetate was
the second most effective with a mean mass of brass created of 0.253 +/- 0.010 g. Following
it was zinc sulfate with a mean mass of brass created of 0.209 +/- 0.010 g, zinc strips with a
mean mass of brass created of 0.141 +/- 0.010 g, and the negative control treatment of no
zinc with a mean mass of brass created of 0.0.003 +/- 0.010 g.
The results of this experiment do not support the original hypothesis that it would be the
zinc strips that would be the most effective zinc sample. In fact, it was the zinc strips that
were the least effective, other than the negative control. The sample that was the most
effective was the zinc dust, meaning that zinc dust should be used in the production of brass
for industrial and commercial purposes in order in increase the yield of brass production in
these fields.
The reasons behind the results failure to support the hypothesis most likely are based in
the form and the concentration of zinc in the mixtures. For example, zinc dust was the most
effective, most likely because of its powdered form and also, because it was one of the most
concentrated suspensions. Its powdered form allowed the zinc dust to freely flow in the
mixture, causing it to be able to act upon the most surface area of the copper. It was the most
concentrated suspension because there were no other chemicals that were originally bonded

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to the zinc, decreasing the energy needed to plate the zinc onto the copper. This is because
there would be energy required to split the zinc ions away from the other chemical in the
compound, as such was the case with the zinc sulfate and the zinc acetate. Because there was
less energy required by the ionization of zinc atoms, more zinc ions could be produced and
the increased surface area of the zinc dust dissolved in the 0.5M NaOH allowed the increased
number of ions to be able to act more directly upon the copper. All these factors made the
zinc dust the most effective sample.
In the trials of zinc sulfate and zinc acetate, both had the increased surface area because
they were able to be dissolved into the 0.5M NaOH mixture, however, as stated above, they
had other chemicals in them. This meant that more energy had to be expended to ionize the
zinc than if it had just been plain zinc, causing there to be less energy to make the ions of
copper and zinc bond together. This decreased amount of energy caused decreases in the
amount of brass that was produced.
In the trials involving zinc strips, there were two major factors that caused the trials to be
very ineffective. The first factor was that the strips were solid sheets of metal, meaning that
the strip had to be directly touching the copper for it to be at its most effective. However, this
presented a problem. In the zinc dust trials, the continuous movement of the mixture allowed
the ions that had been reduced to go somewhere and for new ions to come and react with the
copper. With a solid and insoluble zinc strip, there was no movement of new ions that could
react with the copper because the reduced ions could not move and so stayed in continuous
contact with the already plated copper. Because the reduced ions could not continue to plate
onto the copper, it was only the zinc ions that were directly touching the copper initially that

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could be plated onto it, which was a very limited amount compared to the amounts of zinc
ions that could be plated onto the copper in the trials of the other samples.
The negative control of no zinc had extremely little brass formation as there was little to
no zinc within the mixture. If there is no zinc in the mixture, then there cannot be any brass
formation because there cannot be a reaction without both the reactants being present. Any
brass formation can be explained by the uncertainty (+/- 0.010 g), which is more than the
amount of brass that was supposedly created.
The errors in this experiment involve both random and systematic error as a result of the
procedure and unforeseen circumstances. Systemic errors in this experiment include when
the mixture reached 100oC, it boiled. Therefore, during the duration of the testing, portions of
the mixture evaporated and were converted in a gaseous form, leaving less mixture, and
therefore, a more concentrated mixture. This caused there to be a larger yield than there
would have been if the mixture had not evaporated. Another systematic error was in the use
of the balance to measure the initial mass of the copper and the final mass of the brass. The
balance had flap that should have been closed to prevent the air flow from affecting the mass
that was measured, however due to the size of the weigh boat that was used, closing the flap
was not possible and so gave a slight error in the initial mass of the copper and the final mass
of the brass.
Ways to fix the systematic error would to keep the mixtures just under boiling, at around
98oC so that the heat required for the reaction to take place would be present, but it would not
be so hot that the mixture would begin to evaporate. In addition, one could use a smaller

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weigh boat for the sample in order to be able to close the balance flap, reducing the air flow’s
effect upon the masses that were measured.
Random error for this experiment includes the measurements of the mixtures through the
use of a graduated cylinder. Liquid mixtures are to be measured at the meniscus, but
depending on the height at which the graduated cylinder is held, the meniscus can be viewed
at different points, therefore increasing the uncertainty of the measurement and causing the
error. Another random error is that when the mixture boiled, sometimes an indeterminable
amount of mixture would bubble over, leaving less liquid in the mixture and a more
concentrated mixture.
A way to reduce the random error in this experiment is to measure the liquid mixtures
using the graduated cylinder at the same height for each measurement so that the meniscus is
always viewed at the same height. However the best way to reduce the random error would
be to complete more trials so that the erroneous data would be averaged out.
Overall, what has been learned in this experiment is that zinc dust is the most effective
zinc sample in the plating of zinc onto copper and the subsequent creation of brass. As such,
what has been determined is that the zinc dust should be used in the production of brass in
industrial and commercial ventures to increase the yield of brass production in these fields.
Expansions of this experiment would include testing other zinc samples against zinc dust
in order to further determine that zinc dust is the optimal chemical for brass production. In
addition, different states of zinc dust could be used, such as melted zinc in order to determine
if the state of zinc has a significant effect upon the brass yield. Furthermore, the source of
energy for the reaction could also be determined. Instead of heat energy being used, electrical

19
energy could be used to power the reaction. This would be done by creating two electrical
poles in the mixture by placing in two wires attached to a battery, creating a current. Copper
would be attached to one and zinc to the other. All of these expansions would be for the
purpose of further determining the optimal process for brass production.
Word Count: 3923
VIII. LITERATURE CITED
Encyclopedia Britannica. (2013) Brass (alloy). Retrieved from -----------------------------------------
----------http://www.britannica.com/EBchecked/topic/77876/brass.
Encyclopedia Britannica. (2013) Zinc Group Element. Retrieved from:
http://www.britannica.com/EBchecked/topic/657321/zinc-group-element
Encyclopedia Britannica. (2013) Copper-Cu. Retrieved from:
http://www.britannica.com/EBchecked/topic/136683/copper-Cu.
Nuffield Foundation. (2008) Turning copper coins into ‘silver and gold’. Retrieved from
http://www.nuffieldfoundation.org/practical-chemistry/turning-copper-coins-silver-and-
gold.
Szczeoankiewicz, S.H. (1995). The "Golden Penny" Demonstration: An Explanation of the Old
---------Experiment and the Rational Design of the New and Simpler Demonstration. Retrieved --
---------from: http://pubs.acs.org/doi/pdf/10.1021/ed072p386

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The Science Company. (2013) Turning Copper Pennies Into Silver and Gold Pennies. Retrieved
from http://www.sciencecompany.com/Turn-Copper-Pennies-Into-Silver-and-Gold-
Pennies-W194.aspx.
McClure, M. R. (2009) Copper. Retrieved from: ----------------------------------------------------------
--------http://www.uncp.edu/home/mcclurem/ptable/copper/cu.htm
Winter, Mark (2012) Zinc. Retrieved from: http://www.webelements.com/zinc/

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IX. APPENDIX
Table 4: Raw date of initial and final masses for each sample.
Sample Trial Number Initial Mass
(+/- 0.001 g)
Final Mass
(+/- 0.001 g)
Zinc acetate 1 0.494 0.598
2 0.521 0.627
3 0.497 0.596
4 0.457 0.558
5 0.501 0.606
Zinc dust 1 0.499 0.712
2 0.486 0.702
3 0.487 0.692
4 0.461 0.673
5 0.493 0.697
Zinc sulfate 1 0.508 0.588
2 0.482 0.568
3 0.484 0.568
4 0.522 0.607
5 0.543 0.631
Zinc strips 1 0.532 0.588
2 0.603 0.662
3 0.611 0.671
4 0.528 0.595
5 0.532 0.587
No zinc 1 0.522 0.524
2 0.533 0.535
3 0.563 0.564
4 0.452 0.453
5 0.573 0.574
Table 5: P-values of trials
Sample P-value
Zinc acetate 6.74E-08
Zinc dust 8.02E-08

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Zinc sulfate 1.04E-07
Zinc strips 8.77E-08
No zinc 1
Sample Calculations:
Calculation of change in mass:
Final mass – Initial mass = Final mass
0.598 +/- 0.001 g - 0.494 +/- 0.001 g = 0.104 +/- 0.002 g
Calculation of mean of brass
Mass1 + Mass2 + Mass3 + Mass4 + Mass5/ 5 = Mean
0.255 + 0.260 + 0.243 + 0.248 + 0.258/ 5 = 0.253 g

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