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Electrolytic Cell

High schoolChemistryConstant-resistance electrolytic cells with reaction-onset voltages, Faraday stoichiometry and finite copper inventory

Click the orange circuit contact, then run the supply. Drag the gap handle, swap polarity or compare copper and inert anodes.

3D

Drag the apparatus to adjust it. Drag the background to rotate. Scroll to zoom.

Measurement notebook

Change the setup, test a prediction and save the result. Up to 12 snapshots are kept.

About this experiment

Wire a virtual electrolytic cell and compare copper sulfate with inert or soluble copper anodes, then switch to water splitting in sodium sulfate. Measure charge, deposited copper and gas volumes while changing gap, area and voltage.

Learning goals

  • Locate oxidation at the positive anode and reduction at the negative cathode.
  • Relate product amounts to charge rather than voltage alone.
  • Explain the role of a soluble copper anode.

How to use it

  1. 1Close the circuit contact and run the supply. Record current and products after a fixed exposure.
  2. 2Increase electrode gap while holding the other settings fixed and compare current.
  3. 3Switch from an inert anode to a copper anode and compare the ion concentration.
  4. 4Reverse polarity and identify where reduction and oxidation move.

The model

Supply-on exposure and the assumed constant current determine charge.
Copper deposition and soluble-anode loss each exchange two electrons per copper atom.
The sulfate water-splitting case produces twice as much hydrogen as oxygen.

Assumptions

  • Resistance is an illustrative fixed function of initial concentration, area and gap; it does not resolve electrode kinetics or changing conductivity.
  • Reaction onset is 1.5 V for copper deposition with an inert anode, 0.2 V for soluble-copper transfer and 1.8 V for the water-splitting case. These are model settings rather than universal thresholds.
  • All current produces the listed reaction products. Inert-anode copper deposition stops when Cu²⁺ is exhausted, rather than switching to a different cathodic reaction.
  • The soluble copper anode starts with 2 g. Gas volumes use 298.15 K and 1 bar. Electrode appearance is schematic.

Try this in class

  1. Q1Why does a soluble copper anode preserve the ideal bath copper-ion concentration?
  2. Q2What changes when the source polarity is reversed?

Frequently asked questions

Does opening the circuit erase collected products?

No. The exposure clock pauses and current becomes zero while the already produced copper and gas remain.

Will a real cell always stop when copper ions are exhausted?

Other reactions can take over in a real cell. This model deliberately stops instead of adding an unmodelled product pathway.