Bio Research

Experiment 9/5 Voltaic cells

AIM
How the change the concentration of the electrolyte CuSo4 (solution of ions) affect the voltage of the electrochemical cell

BACKGROUND
An electrochemical cell is also called a voltaic cell, which derives electrical energy from redox reaction taking place within the cell. It consists of two different metals that are connected by a salt bridge. Eletrons always flow from anode to cathode, where anode is negative (reduction) and cathode is positive (oxidation). A lot of factors may affect the voltage of an electrochemical cell, such as the change in concentration of the solutions.

INDEPENDENT VARIABLE: Concentration of the CuSo4 Solution

DEPENDENT VARIABLE: Voltage of electrochemical cell

CONTROLLED VARIABLE: Temperature of surrounding (room temperature), Temperature of solutions, Volume of solutions (100mL), Concentration of ZnSo4 (0.1 mol), Concentration KNO3 (1 mol), Type of filterpaper, Mass of zinc and copper electrode

APPARATUS

• Digital Voltmeter
• 2 beakers 100mL
• 2 Conductivity Cups
• Filterpaper
• Wires 2x
• Crocodile clips 2x
• 100mL of 0.1 mol ZnSo4 Solution
• 100mL of CuSo4 Solution with the following concentrations
- 0.1 mol
- 0.3 mol
- 0.5 mol
- 1 mol
- 2 mol
• 1 mol of KNO3 Solution
• Zn strip 5x
• Cu strip 5x
• Thermometer
• Multimeter

DIAGRAM

METHOD

1. Measure the room temperature by using a thermometer. All experiments are carried out at the same room temperature.
2. Measure the temperature of ZnSo4 and CuSo4 solution by using a multimeter at room temperature. Keep the temperature of the solutions constant.
3. Use a beaker to measure 100mL of 0.1 Mol ZnSo4 Solution.
4. Fill the solution of 100ml 0.1 Mol Zinc sulphate (ZnSo4) solution into one conductivity cup.
5. Use a beaker to measure 100ml of 0.1 mol CuSo4 solution.
6. Fill the solution of 100ml 0.1 mol Copper Sulphate (CuSo4) solution into the second conductivity cup.
7. Put a piece of Zinc into the ZnSo4 solution
8. Put a piece of Copper into the CuSo4 solution.
9. Soak filterpaper into KNO3 until the filterpaper is completely saturated
10. Construct a saltbridge by placing the filterpaper across the two beakers filled with the solution.
11. Plug in two wires into the voltmeter and put a crocodile clip on each end of the wire
12. Connect one wire to the Zn strip and one wire to the Cu strip.
13. Read the voltage from the digital voltmeter
14. Record the data
15. Change the concentration of CuSo4 and repeat the experiment (steps 2-14).
16. Use a new piece of Zn strip and Cu strip for each new experiment
17. Use a new piece of filterpaper, but the same type, for each new experiment.
18. Repeat the experiment (steps 2-14) until all 5 different concentrations have been tested
- 0.3 mol
- 0.5 mol
- 1 mol
- 2 mol