Chemistry
Electrochemical Series and the Prediction of Redox Reaction Spontaneity
Quick fact
The electrochemical series ranks half-reactions by their standard reduction potentials (E°). Simply by comparing two half-reactions, you can instantly tell whether a reaction is spontaneous: the reaction proceeds if the overall cell potential (E°cell = E°cathode - E°anode) is positive, which corresponds to a negative Gibbs free energy change. This series is to redox reactions what a ruler is to height.
Why this is interesting
Imagine two metals in a beaker of salt water: one slowly disappears, the other is protected. How can you predict which metal will react and which will stay inert, without ever running the experiment?