Uncertainty of mass = 0.01 g
Percent uncertainty of mass =
Percent uncertainty of mass =
Percent uncertainty of mass ≈ 1.89%
The percent uncertainty for the number of moles is approximately 1.89%. Thus, the number of moles is approximately 0.00834 ±1.89%.
Current:
Average charge = Average current x time
After 10 minutes
Average current =
Average current = 0.9 A
Percent uncertainty of average current =
Percent uncertainty of average current ≈ 11.1%
The percent uncertainty for the average current is approximately 11.1%. Thus, the average current after 10 minutes is 0.9 A ±11.1%.
After 20 minutes
Average current =
Average current = 0.8 A
Percent uncertainty of average current =
Percent uncertainty of average current ≈ 12.5%
The percent uncertainty for the average current is approximately 12.5%. Thus, the average current after 20 minutes is 0.8 A ±12.5%.
After 30 minutes
Average current =
Average current = 0.95 A
Percent uncertainty of average current =
Percent uncertainty of average current ≈ 10.5%
The percent uncertainty for the average current is approximately 12.5%. Thus, the average current after 20 minutes is 0.95 A ±10.5%.
Time:
Time = 60 seconds x 10 minutes
Time = 600 seconds
Percent uncertainty of time =
Percent uncertainty of time ≈ 0.833%
The percent uncertainty for time is approximately 0.833%. Thus, the time after 10 minutes is 600 seconds ±0.833%.
Charge:
After 10 minutes
Average charge = average current x time
Average charge = 0.9 A x 600 seconds
Average charge = 540 C
Percent uncertainty of average charge = Percent uncertainty of current + Percent uncertainty of time
Percent uncertainty of average charge = 11.1% + 0.833%
Percent uncertainty of average charge ≈ 11.9%
The percent uncertainty for average charge is approximately 11.9%. Thus, the average charge is approximately 540 C ±11.9%.
After 20 minutes
Average charge = average current x time
Average charge = 0.8 A x 600 seconds
Average charge = 480 C
Percent uncertainty of average charge = Percent uncertainty of current + Percent uncertainty of time
Percent uncertainty of average charge = 12.5% + 0.833%
Percent uncertainty of average charge ≈ 13.3%
The percent uncertainty for average charge is approximately 13,3%. Thus, the average charge is approximately 480 C ±13.3%.
After 30 minutes
Average charge = average current x time
Average charge = 0.95 A x 600 seconds
Average charge = 570 C
Percent uncertainty of average charge = Percent uncertainty of current + Percent uncertainty of time
Percent uncertainty of average charge = 10.5% + 0.833%
Percent uncertainty of average charge ≈ 11.3%
The percent uncertainty for average charge is approximately 11.3%. Thus, the average charge is approximately 570 C ±11.3%.
Total charge = Sum of all 3 average charges
Total charge = 540 C + 480 C + 570 C
Total charge = 1590 C
Absolute uncertainty of total charge =
Absolute uncertainty of total charge = 192.51
The total charge is 1590 C ±192.5 C.
Avogadro’s Number Calculations:
number of electrons = 9.9375 x 1021
Uncertainty of number of electrons:
The total number of electrons is 9.9375 x 1021 ±1.203 x 1021.
Number of atoms:
number of atoms ≈ 4.969 x 1020
The total number of atoms is approximately 4.969 x 1020.
Avogadro’s number:
Avogadro’s number ≈ 5.96 x 1023
Avogadro’s number is approximately 5.96 x 1023.
Percent error:
≈ -0.997% error
Conclusion and Evaluation
In this experiment, a copper electrode was connected to a power source to create a copper plating cell. The electrons flowed from the power source to through a cathode to the copper sulfate solution, where the copper ions reacted with electrons to be converted to copper metal. The copper metal atoms were then deposited onto the cathode. In this experiment we had both a cathode (Electrode 1) and an anode (Electrode 2). In the anode, one atom is ionized and dissolved into the solution from the anode for every copper atom is deposited on the cathode. The gain or loss of mass of each electrode can then be divided into the molar mass of copper, which will then equal the number of moles of reacted copper. The length of time and the amps of current, when multiplied, equal the total amount of charge.
The electrode where the oxidation reaction takes place (loss of mass) is the anode, and the electrode that gained mass is the cathode. The anode (Electron 2) gained copper electrons, and the cathode (Electron 1) lost copper electrons. The copper electrons in the cathode move from the negative end to the positive end, and thus the reaction takes place.
In our experiment, I noticed that the anode was rusty and thinner because it lost electrons. This theory is proven by the weights we recorded in the experiment; the final mass of Electrode 2 was less than the initial mass.
There were several errors in this experiment. First, the electrodes were only given a few seconds to dry before we weighed them. An error could have occurred by having an increase in mass because there was still acetone or water on the electrodes. This can be improved by letting the electrodes dry fully before being weighed.
Another important error, which would have had major effects on the results, is human error. If any of the calculations were incorrect, then the results would not match up with Avogadro’s number.
