3B Scientific Electrochemistry Kit - Manual (Page 20)

21
Experiment 7 - Measuring voltage Student instructions
Measuring the voltage of a zinc-carbon (Leclanché) cell
Chemicals Hazard
symbols
R phrases S phrases Equipment
Meter
Graphite powder --- --- Electrodes:
1 C, 1 Zn
Manganese (IV) oxide 20/22 25 2 Experiment cables
Ammonium chloride 22-36 22 1 Plastic beaker
Distilled water --- --- 2 Pipettes
Warning: Be careful when handling chemicals!
Experiment procedure:
1. To assemble a zinc-carbon or Leclanché cell a 20% ammonium chloride solution and some depolarizing paste are
required. These should be given to the students.
2. Assemble the battery block as described.
3. Fill one chamber each with 20% ammonium chloride solution and insert the zinc electrode. Fill the chamber opposite
with a depolarizing paste consisting of graphite powder, manganese (IV) oxide (battery manganese) and ammonium
chloride solution and insert the carbon electrode. The depolarizing paste is there to prevent hydrogen forming at the
carbon electrode.
4. Connect the two electrodes to the meter using 2 experiment cables with crocodile clips and measure the voltage
generated by the Leclanché cell.
Observation and evaluation:
Sketch of experiment set-up:
Results of voltage measurement:
The Leclanché cell supplies a voltage of V.