Measuring the Effects of Current on the Change in Mass of a Penny and a Quarter During Electrolysis
Purpose:
The objective of this lab is to determine the effect of amperage on the change in mass of a
quarter (cathode) and a penny (anode) during electrolysis in a .1M copper (II) sulfate solution by
creating a electrolytic cell.
Hypothesis:
As amperage increases then the change in mass will increase. The rationale for this hypothesis is
because as more electrons flow through the electrolytic cell the more ions will be reduced or oxidized.
Variables:
Independent Variable: Amperage (0.06; 0.08; 0.1; 0.12; 0.14)
Dependent Variable: Change in mass of the quarter (cathode) and the penny (anode)
Controlled Variables: Temperature, Concentration of solution, Surface area of cathode and
anode, Amount of solution, Distance between anode and cathode, and Time
Temperature was controlled by performing the experiment in the same room on the same day
when temperature was the same. The concentration of the solution was controlled by creating and
using a .1M solution of copper (II) sulfate. The Surface area of the cathode and anode were controlled by
measuring the midline of each coin, marking it, and then dipping one half below the solution. The
amount of solution was controlled by using a graduated cylinder to measure out 100mL of solution. The
distance between the anode and the cathode was controlled by taping the coins to the wall of the
beaker at their furthest point apart (7 cm). Time was controlled by leaving the current on for 1 minute at
each increment for each test.
Materials:
15 U.S Quarter
15 U.S Penny (Minted Prior to 1982)
250mL Beaker
500mL Distilled Water
12.4843g Copper (II) Sulfate (F.W of 249.685g)
Ammeter
75W AC/DC Power Supply
Rubbing Alcohol
Masking Tape
100mL Graduated Cylinder
500mL Volumetric Flask
Digital Balance
1 Banana Plug Wires (Red)
Alligator Clip to Banana Plug Probe Cables (1 Red, 1 Black)
Paper Towels
Permanent Marker
Stopwatch
Procedure:
1. 500mL of distilled water was measured out in a 500mL volumetric flask.
2. 12.4843g of copper (II) sulfate pentahydrate was measured out using the digital balance. It
was then poured into the volumetric flask, covered, and then mixed thoroughly.
3. All pennies and quarters were cleaned using rubbing alcohol and a paper towel to get off
any surface grime or dirt.
4. The midline of each quarter and penny was then measured and marked using a permanent
marker. The diameter of the penny was 19mm and the quarter was 24mm.
5. The mass of each penny and quarter was each measured and recorded. The coins were then
placed on a paper towel one at a time after being weighed and numbered in pairs with their
initial masses written underneath.
6. Next, the electrolytic cell was put together using the power supply, all 3 wires, the ammeter,
the 250mL beaker, and the masking tape.
a. First, the power supply was placed on the lab bench and the black alligator clip to
banana plug probe cable was plugged into the black (negative) dc plug on the power
supply.
b. Then the red banana plug probe to banana plug probe cable was plugged into the
red (positive) dc plug on the power supply. The other end was then plugged into the
.1A plug of the ammeter.
c. The remaining wire, the red alligator clip to banana plug probe, was then plugged
into the outlet plug of the ammeter.
d. Next, the beaker was filled with 100mL of the .1M solution of copper (II) sulfate.
e. The two alligator clips wires were then taped to the rim of the beaker at the furthest
point apart (7cm) so that the clips hung down to just above the solution.
7. A penny was then attached to the red (positive) alligator clip and submerged in the solution
to its midline.
8. A quarter was then attached to the black (negative) alligator clip and submerged in the
solution to its midline.
9. The power supply was then plugged in and turned on. The knob was then turned until the
amperage reached .06 amps on the ammeter and the stopwatch was started. After 1 minute
the power supply was turned off.
10. The coins were then removed from the solution and placed on a paper towel to dry. Once
dried their mass was then measured and recorded. This process was then repeated so that
there were 3 trials for this increment.
11. The solution was then disposed of and refilled by another 100mL of the .1M copper (II)
sulfate solution for a new increment.
12. Steps 7 to 11 were then repeated for increments 0.08; 0.10; 0.12; and 0.14
Diagram:
Raw Data:
Raw Data for Electroplating
of a Quarter
0.06 Amps (Amperes)
(±0.005)
0.08 Amps (Amperes)
(±0.005)
0.10 Amps (Amperes)
(±0.005)
0.12 Amps (Amperes)
(±0.005)
0.14 Amps (Amperes)
(±0.005)
Initial Mass of
Number Penny (g)
of Trial (±0.0001g)
Final Mass of
Penny (g)
(±0.0001g)
Initial Mass of
Quarter (g)
(±0.0001g)
Final Mass of
Quarter (g)
(±0.0001g)
Trial 1
Trial 2
Trial 3
3.1429
3.1218
3.1039
3.1418
3.1202
3.1026
5.5796
5.7292
5.6831
5.5812
5.7311
5.6849
Trial 1
Trial 2
Trial 3
3.1064
3.0342
3.0842
3.1041
3.0323
3.0822
5.7121
5.7021
5.6544
5.7156
5.7144
5.6570
Trial 1
Trial 2
Trial 3
3.0898
3.1253
3.0993
3.0871
3.1228
3.0967
5.5796
5.5938
5.5961
5.5825
5.5965
5.5988
Trial 1
Trial 2
Trial 3
3.0667
3.1358
3.0951
3.0641
3.1325
3.0921
5.7085
5.6839
5.5435
5.7116
5.6885
5.5473
Trial 1
Trial 2
Trial 3
2.9868
3.0802
3.0683
2.9836
3.0770
3.0644
5.5833
5.7692
5.6673
5.5876
5.7741
5.6718
Observations:
At the end of each trial, the penny had a lighter color and was visibly stripped of some of
its surface. The quarters for each trial had plating; however, past 0.06 amps the color was black
instead of the copper color. At 0.10 amps and up there was precipitation around the quarter;
however, it didn’t plate to the quarter and was floating around in solution.
Processed Data:
Change in Mass of the
Penny and Quarter
Following Electrolysis
0.06 Amps (Amperes)
(±0.005)
0.08 Amps Amps
(Amperes) (±0.005)
0.1 Amps Amps (Amperes)
(±0.005)
0.12 Amps (Amperes)
(±0.005)
0.14 Amps Amps
(Amperes) (±0.005)
Change In
Mass of
Number Penny (g)
of Trial (±0.0002g)
Change In
Mass of
Quarter
(g)
(±0.0002g)
Trial 1
Trial 2
Trial 3
-0.0011
-0.0016
-0.0013
0.0016
0.0019
0.0018
Trial 1
Trial 2
Trial 3
-0.0023
-0.0019
-0.0020
0.0035
0.0023
0.0026
Trial 1
Trial 2
Trial 3
-0.0027
-0.0025
-0.0026
0.0029
0.0027
0.0027
Trial 1
Trial 2
Trial 3
-0.0026
-0.0033
-0.0030
0.0031
0.0046
0.0038
Trial 1
Trial 2
Trial 3
-0.0032
-0.0032
-0.0039
0.0043
0.0049
0.0045
Average Change In Mass of the
Penny and the Quarter Following
Electrolysis
0.06 Amps (Amperes) (±0.005)
0.08 Amps (Amperes) (±0.005)
0.1 Amps Amps (Amperes)
(±0.005)
0.12 Amps (Amperes) (±0.005)
0.14 Amps Amps (Amperes)
(±0.005)
Average
Average
Change In
Change In Mass of
Mass of
Quarter
Penny (g)
(g)
(±0.0002g) (±0.0002g)
-0.0013
0.0018
-0.0021
0.0028
-0.0026
-0.0030
0.0028
0.0038
-0.0034
0.0046
Conclusion:
The purpose for doing this experiment was to determine the effect of current
(amperage) on the electroplating of a quarter using a penny and .1M copper (II) sulfate solution.
The data above suggests that as current increases the mass plated on the quarter increases. This
is what was originally hypothesized. The data in the above graphs appears to have a general
linear trend suggesting a direct relationship, however since as current increased there was some
mass that was lost to solution this isn’t certain. Using the mass lost by the penny would better
suggest a linear relationship between the current and the mass lost/plated.
Evaluation and Improvements:
There are several weaknesses to this experiment. These include human error, random error,
procedural error, and measurement error. The first of these, human error, came into play in the creation
and execution of the electrolytic cell. While the attempt was made to keep the distance between and
the surface area of the two coins constant; it was difficult to do so because over time the tape
weakened, or occasional bumps to the table resulted in changes to these variables. This error could be
eliminated or reduced by completely submerging the coins into solution to keep the surface area
constant as well as using clamps to keep the wires in place instead of tape which sagged over time and
the distance between the two coins changed.
Random error occurred during the actual time that the power supply was on. This error includes
that the needle of the ammeter would fluctuate randomly and the power supply would have to be
adjusted mid trial; also there was random error in the trials in which some mass precipitated but didn’t
stick to the quarter, this caused false values. The first type of error could be improved by using a digital
ammeter or power supply to control amperage instead of a manual one. The second error could be
improved by using wire mesh or a spatula to fish out the precipitate and add that to the weight change.
Procedural error could have occurred during the creation of the .1M copper (II) sulfate solution
as well as the cleaning of the coins. The solution appeared to be settling over time and perhaps could
have changed by the time the beaker was refilled for the later trials; the coins could have differed in
their cleanliness which would result in varying surface area that was clean. The certainty of the solution
could be improved by creating it as needed for each trial or by using a test to check its molarity. The
cleanliness of the coins could have been improved by being more thorough in cleaning.
Lastly, measurement error could have occurred in the weighing of the coins and in the
measuring of their surface area. The measuring of the weight of the coins could have been improved by
using a more accurate scale, by allowing them to air dry over time, and by adding the lost precipitate to
the quarter for final measurement. The measuring of the surface area exposed to solution could have
been better measured by using calipers or by simply entirely submerging the coins in solution.