Electrochemical Cell Builder
Pick two metals, dip them in solutions of their ions and join them with a wire. The one that gives up electrons more easily becomes the anode, and the cell makes a voltage.
How a galvanic cell works
Each metal has a standard reduction potential E°. The metal with the lower E° is oxidised at the anode (−): it loses electrons, which flow through the wire to the cathode (+), where metal ions are reduced and plated out. The salt bridge lets ions move to keep both beakers neutral. E°cell = E°cathode − E°anode; for the Daniell cell (Zn | Cu) it is 0.34 − (−0.76) = 1.10 V.
The Nernst equation
Concentrations matter too. At 25 °C, Ecell = E°cell − (0.0592 / n) log Q, where n is the number of electrons transferred and Q is the reaction quotient. The cell's energy is ΔG = −nFE: a positive E means the reaction is spontaneous. When the cell is flat, E = 0 and Q has reached the equilibrium constant K. Try two pieces of the same metal at different concentrations: a concentration cell!
Standard reduction potentials at 25 °C (V): Mg²⁺/Mg −2.37, Zn²⁺/Zn −0.76, Fe²⁺/Fe −0.44, Ni²⁺/Ni −0.25, Pb²⁺/Pb −0.13, Cu²⁺/Cu +0.34, Ag⁺/Ag +0.80. Concentration sliders are logarithmic.