The Good Chemist's Guide: Copper

Welcome chemists!!!
As promised, here's our weekly experiment. This experiment has been carried out after having learned about REDOX reactions.

JUST BEFORE THE START

This is a good rule to remember REDOX reactions: OIL RIG (Oxidation is Loss of electrons and Reduction is Gain of electrons)!! Oh, by the way... Just in case you don't know about that REDOX stuff... Here's a fantastic website which explains it perfectly.

BACKGROUND INFORMATION:

"The flow of current is the flow of ions from the more reactive metal to the less reactive metal. The ions moving from one electrode to the other creates an electrical charge which is neutralised by the flow of electrons across the wire.

When we place a single metal electrode in an electrolyte some of the metal atoms in the electrolyte go into solution as ions while the remaining electrons create a negative charge on the metal. The separation of ions and electrons leads to a separation of charge. However, this build up of charge cannot continue indefinitely because as the negative charge builds up in the metal it becomes increasingly difficult for positive metal ions to go into solution. A similar build up in positive charge in the electrolyte also prevents the build up of charge. This degree of charge build up depends on the metal and represents the work required to separate electrons from the ions. This is known as the electroneutrality principle.

If a copper strip is placed in an aqueous copper (II) sulfate solution the copper will also lose ions. These reactions are often written as Cu⁺² | Cu this is the half-cell reaction. The tendancy for zinc to lose ions is greater than that of copper. When the two cells are joined together, the build up of electrons on the zinc will flow to through the wire onto the copper. " - Reference 1

AIM: To create a battery, obtaining energy from two redox couples with the use of a salty bridge (ionic bond) as an intermediary.

MATERIALS: REACTANTS:

- 100 mL beaker (x2) - 20 mL of 1M CuSO4 + 60 mL of H2O
- U-Tube - 20 mL of 1M ZnSO4 + 60 mL of H2O
- Multimeter
- Cotton
- Strip of zinc
- Strip of copper
- Salty water (NaCl + H2O)
- Water

PROCEDURE

1.- Pour 20 mL of 1M CuSO4 and 60 mL of H2O in one beaker.

2.- Pour 20 mL of 1M ZnSO4 and 60 mL of H2O in a different beaker.

3.- Create a salty bridge by filling 1/3 with salty water (NaCl + H2O) and the rest with water. Create stoppers by locating 2 cotton pieces at each end of the salty bridge.

4.- Clamp the copper string, using the voltmeter clamp, and place it into the copper solution. The clamp itself must not make contact with the solution. Do the same with the zinc strip in the zinc solution.

5.- Switch the multimeter on.

6.- Make a connection between the two beakers with the salty bridge, by placing one of the arms inside the copper solution and the other one inside the zinc solution.

7.- A charge will be recorded in the multimeter. Collect the data.

RESULTS: We obtained 14,32 millivolts in the multimeter.

Conclusions related with the results: When the U-tube containing the salty solution was absent, there was no reading on the multimeter, whereas when the salty bridge connected the two solutions, a number was recorded on the multimeter. The direction of the flow of electrons goes from the zinc beaker to the copper beaker.

CONCLUSION:

As a conclusion, it is possible to create a battery out of two REDOX couples.

Redox couples are willing to give energy, as it has been demonstrated. We have been able to create a copper - zinc galvanic cell with zinc and copper REDOX couples.

2+ 2+
Cu / Cu Zn / Zn

As the image shows, and knowing the standard reduction potentials for the two half-cells given at the bottom of the following image :

Image reference 1

We can therefore deduce that the copper strip is the cathode and the zinc strip is the anode. To conclude, when a copper sulphate solution, connected to a copper strip, and a zinc sulphate solution, connected to a zinc strip, are connected by a salty bridge, a reaction will occur in each of the sides or beakers. The chemical energy produced by the redox couples has been transformed into electrical energy.

$\text{[math]}$