Galvanic Electrochemical Cells

Philip Chun General Physics

Galvanic Electrochemical cells Background: The type of reaction that occurs in the galvanic electrochemical cells is called a redox reaction. Redox reactions take place in electrochemical cells. The type of cell that we are experimenting with is called a voltaic cell, because the reaction occurs spontaneously. These electrochemical cells, if joined together in series are called a battery. To connect several cells together we can connect the anode and the cathode to another cell’s anode and cathode using either alligator clips or wires. Also there must be a salt bridge between the two half cells because without the salt the build up of positive charge would stop the flow of negatively charged electrons away for the half-cell. The salt bridge is used to complete the circuit. Now batteries are used everyday, in radios, cars, or anything that can fit a standard AA, AAA etc. All the new batteries can trace their ancestry to the galvanic electrochemical cells. Aim: To determine if the concentration of the Zinc Sulfate and Copper Sulfate solution affect the amount of voltage created by the battery cell. Hypothesis: The concentration should affect the amount of voltage created. Materials: 200 ml of .5 M ZnSO4 200 ml of 1. M ZnSO4 200 ml of 2. M ZnSO4 200 ml of .5 M CuSO4 200 ml of 1. M CuSO4 200 ml of 2. M CuSO4 6 250 ml beakers Paper towels Safety goggles Distilled Water Salt (NaCl will do fine) 3 pure Zinc strips 3 pure Copper strips Multimeter 2 Graduated cylinders 6 Alligator clips Variables: Independent: volume of solution Dependent: moles of each solution Procedure: 1. Wearing your safety glasses, measure out 100 ml of each solution and pour them into separate beakers. 2. Measure out 100 grams of NaCl and mix it into the distilled water to make a super concentrated salt solution

Philip Chun General Physics 3. Make a salt bridge for the reaction by rolling the paper towels and submerging it in the concentrated salt solution. 4. Place one end of the salt bridge in the .5 M ZnSO4 solution and the other in the .5 M CuSO4 solution 5. Clip one end of the alligator clips to the Zinc strip and one end to the multimeter 6. Clip one end of the alligator clips to the Copper strip and one end to the multimeter 7. Put the zinc strip into the .5 M ZnSO4 solution 8. Put the copper strip into the .5 M CuSO4 9. Read the voltage on the multimeter 10.Repeat steps 2-9 replacing the .5 M solutions to the 1 M solution and the 2 M solution. Setup: Figure 1:

Data: Qualitative: The reaction that occurred between the two solutions was spontaneous. After cleaning out the beakers I noticed that salts had formed( ZnCl2 and CuCl2). The two solutions were constantly reacting causing the multimeter reading to change frequently ( I had to wait a few minutes for the multimeter to settle on one number)

Philip Chun General Physics

Quantitative: Table 1: Solutions CuSO4 and ZnSO4 CuSO4 and ZnSO4 CuSO4 and ZnSO4

Concentration (M) .5 M 1. M 2. M

Electric Potential (V) 1.058 1.072 1.708

Data Analysis: Given our data it becomes evident that the concentration of the solutions of CuSO4 and ZnSO4 do effect the amount of current produced in the battery. However the change in molarity and the change in electric potential yielded is quite different between the .5 M to the 1. M and the 1. M to the 2. M. The difference between the .5 M and the 1. M is 0.014 volts and the difference between the 1.M and the 2. M is 0.636 volts. Conclusion: As the data shows the initial hypothesis was proved correct. However the difference between the electric potential yields between the .5 M to the 1. M and the 1. M to the 2. M raises some questions. There may have been some type of systematic error because the .5 M and 1. M solutions were conducted with separate cathodes and anodes. While this may have little effect on the overall experiment, this is still a source of error, however small. Also there may have been an inconsistency with the amount of salt added in the salt bridge. This would greatly affect the electric potential yielded because with more salt, there would be more current. This may have caused the dramatic change between the .5 M to the 1. M and the 1. M to the 2. M. Also the type of multimeter may have something to due with the dramatic change because one multimeter may have a greater resistance than the other. To try and improve the accuracy of this experiment, more trials would have to be conducted, however due to some time limitations; I was unable to conduct any further experiments.