3B SCIENTIFIC PHYSICS ELEKTROCHEMIE U11110 ...

Experiment 5 - Measuring voltage Teacher's instructions
Measuring the standard potential of various metals
Chemicals Hazard
symbols
Copper (II)-sulfate-(5 H2O)
Zinc sulfate-(7H2O)
Silver nitrate
Iron (II)-sulfate-(7 H2O)
Hydrochloric acid 1 mol/l
R phrases S phrases Equipment
22-36/38-50/53 22-60-61
Meter
Electrodes:
1 Cu, 1 Zn, 1 Ag, 1 Fe,
1 platinum gauze
36/38-50/53 22-25-60-61 2 Experiment cables
34-50/53 26-45-60-61 1 Mains power supply
22-36/38 24/25 2 Pipettes
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 CuSO4 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 (AgNO3 /
Ag , ZnSO4 / Zn and FeSO4 / Fe).
Observation and evaluation:
Fe Ag Zn Cu
(4) (3) (2) (1)
Pt _ connection
16
3V adapter
+ 230V
For each redox pair, the standard electrochemical potentials as measured should be:
(1) Cu / Cu 2+ = + 0.34 V, (2) Zn / Zn 2+ = - 0.76 V, (3) Ag / Ag + = + 0.80 V, (4) Fe / Fe 2- = - 0.44 V
Calculation of masses required to prepare 1 liter of a 1 molar solution:
1. For a CuSO4 solution 249.50 g of CuSO4⋅ 5 H2O is needed.
2. For a ZnSO4 solution 287.40 g of ZnSO4⋅ 7 H2O is needed.
3. For a AgNO3 solution 169.88 g of AgNO3 is needed.
4. For an FeSO4 solution 277.91 g of FeSO4⋅ 7 H2O is needed.