1. Objective : measuring the voltage changes in ½ cells when concentrations are altered in reaction
hypothese:according to the Nernst equation, changes in concentration should not change
2. Materials : beakers
bare copper wires
copper ions in solution (copper nitrate)
1. Obtain 100mL 1m copper nitrate and serial dilute to obtain concentrations of 0.1M, 0.01M, and 0.001M
2. Obtain ...view middle of the document...
6. Repeat steps 3-5 with each serial dilution.
7. Record voltage readings on the given tables on part 4
concentrations | first reading (volts) | second | average |
1M | 7.4mV | 7.5mV | 7.45mV |
0.01M | 68.8mV | 63.8mV | 66.3mV |
0.001M | 82mV | 80.2mV | 81.1mV |
0.0001M | 93.3mV | 92.5mV | 92.9mV |
0.00001M | 100.5mV | 102mV | 101.25mV |
5. Discussion : write the half-cell reactions as well as the total overall equation for this reaction.
at the anode: Cu(s) -> Cu+2 + 2e-
at the cathode : Cu+2 + 2e- -> Cu(s)
combined: Cu+2 + 2e- + Cu(s) -> Cu(s) + Cu+2 + 2e-
Theoretical vs experimental values
series 1 shows the experimental values collected while series 2 are the values calculated using the known concentrations of copper ion and plugging those values into the Nernst equation.
6. Conclusion: what conclusions can be drawn from the different voltage readings of differing concentrations? The greater the difference in concentrations and the closer the concentration of a ½ cell gets to zero, the higher the voltage reading for a given reaction.