The equation of the line was used to
calculate the concentration of each penny solution by plugging the absorbance
measurements in for “y”.
In Microsoft Excel, the grams of copper that were originally
in the penny were calculated.
The percent Cu for each penny was found in Microsoft
Excel using the mass of each penny.
The mean percent Cu and the standard deviation
were also calculated in Microsoft Excel.
Results
Thomas 4
The concentration and absorbance of each stock solution is displayed in Table 1.
Stock Solution (mL)
Concentration (g/L)
Absorbance
Wavelength (nm)
0.000
0.00

608.00
0.020
2.00
0.256
0.040
4.00
0.431
0.060
6.00
0.564
0.080
8.00
0.711
0.100
10.00
0.989
Table 1: Standard Solution
The calibration curve was found using the linear regression function on
Logger
Pro
.
Calibration Curve for the Standard Solutions
Figure 1
The following table gives the absorbance of each penny that was calculated from the
spectrophotometer.
Penny 2, the penny that was minted most recently (in 2002) has the
highest absorbance.
Absorbance
Thomas 5
Penny 1
0.528
Penny 2
0.538
Penny 3
0.529
Table 2
Table 3 shows the data from the 3 pennies that was calculated using a spreadsheet on
Microsoft Excel.
Year
Concentration
(g/L)
g Cu
Mass (g)
% Cu
Mean % Cu
Standard
Deviation
Penny 1: 1997
0.528
0.0528
2.486
2.12%
2.13%
0.0265
Penny 2: 2002
0.540
0.0538
2.488
2.16%
Penny 3: 1997
0.5298
0.0529
2.507
2.11%
Table 3
The following table shows that statistics test used to compare the currently mandated Cu
content with the results of this experiment.
Average Mass
% Cu
Accepted
Value
TTest Value
at 95%
Confidence
Level
S
m
TTest Right
Side
TTest Left
Side
Significantly
Different
2.13%
2.5
4.3
0.01527
0.0656
0.37
Yes
Table 4
Discussion
The TTest at 95% confidence level indicated that the 2.13% Cu found in the
sample pennies was significantly different than 2.5% Cu predicted in the hypothesis.
While the % mass value determined by the tested pennies was somewhat close to the
accepted value of 2.5%, the TTest suggest that the copper content was not in agreement
Thomas 6
with the accepted value.
This evidence does not support the hypothesis that all pennies
minted after 1982 would contain 2.5% copper content.