Galvanic Cell: Voltage, Electron Flow and Electrode Mass
Pick a metal for each half-cell and set the ion concentrations, temperature and load, and see which electrode is the anode and which the cathode, the cell voltage from the Nernst equation, and electrons moving through the wire while ions move through the salt bridge. As the cell runs, the voltage falls and the two electrodes change in mass by different amounts.
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What you can adjust
- Left electrode
- 0 – 5
- Right electrode
- 0 – 5
- Left ion concentration
- 0.01 – 2 mol/dm³
- Right ion concentration
- 0.01 – 2 mol/dm³
- Temperature
- 278 – 323 K
- Circuit
- 0 – 1
- External resistance
- 1 – 1000 Ω
- Running time
- 0 – 60 min
The metal of the left half-cell, in a solution of its own ions. Whichever metal has the lower reduction potential is oxidised, so it becomes the anode, on whichever side it is drawn.
The metal of the right half-cell. Choosing the same metal on both sides gives a standard cell voltage of 0 V, because the two half-cells have the same reduction potential.
The concentration of the left metal's ions. At 1.00 mol/dm³ the cell voltage equals the standard value. Changing it shifts the voltage a little, following the Nernst equation.
The concentration of the right metal's ions. A lower concentration of the ions that are being used up lowers the voltage, and a low enough concentration runs out during the run.
The temperature of both solutions. It changes the RT/nF term of the Nernst equation; the standard potentials are the values at 298 K.
Closed: a wire and a load resistor join the electrodes, so a current flows and the cell runs down. Open circuit: a voltmeter only, so almost no current flows and nothing changes.
The load resistor in the wire. The current is the cell voltage divided by this plus the cell's internal resistance (taken as 5 Ω, a simplification). A smaller resistance gives a bigger current, so the cell runs down faster.
How long the cell runs with the circuit closed. The charge passed, the mass lost by the anode and gained by the cathode, and the falling voltage all grow with time.