3B Scientific Electrochemistry Kit - Manual (Page 16)

17
Experiment 5 - Measuring voltage Student instructions
Measuring the standard potential of various metals
Chemicals Hazard
symbols
R phrases S phrases Equipment
Meter
Copper (II)-sulfate-(5 H
2
O) 22-36/38-50/53 22-60-61 Electrodes:
1 Cu, 1 Zn, 1 Ag, 1 Fe,
1 platinum gauze
Zinc sulfate-(7H
2
O) 36/38-50/53 22-25-60-61 2 Experiment cables
Silver nitrate 34-50/53 26-45-60-61 1 Mains power supply
Iron (II)-sulfate-(7 H
2
O) 22-36/38 24/25 2 Pipettes
Hydrochloric acid 1 mol/l 36/37/38 26 1 3V adapter
Distilled water --- ---
Warning: Please take care: Salts of heavy metals are poisonous! Hydrochloric acid is corrosive!
Experiment procedure:
1. The prepared 1.0 molar electrolyte solutions should be given to the students. Students require no more than 10 ml of
the relevant solution each.
2. Assemble the battery block as described.
3. Add the 1 molar hydrochloric acid to one chamber of the battery block using the pipette and insert the platinum
gauze electrode into this cell.
4. Add a 1 molar CuSO
4
solution to a second chamber (opposite the platinum gauze electrode) and insert a copper
electrode.
5. To form a normalized hydrogen electrode, a 3V adapter is connected to the power supply. Connect the negative
pole of the 3V adapter to the platinum gauze electrode and the positive pole to the copper electrode using
experiment cables. Connect the power supply to the 230 V mains and electrolyze the platinum gauze for about 30
seconds. Hydrogen forms at the platinum gauze and completely surrounds the gauze.
6. The 3V adapter is then replaced by the meter and the voltage can then be read off.
7. Proceed as in steps 4 to 6 with each of the other metals using the corresponding electrolyte for each metal (AgNO
3
/
Ag , ZnSO
4
/ Zn and FeSO
4
/ Fe).
Observation and evaluation:
Sketch of experiment set-up:
Result of voltage measurement:
Cu / Cu 2+ V
Zn / Zn
2+
V
Ag / Ag
+
V
Fe / Fe
2+
V