Consider a reaction between one halogen—chlorine, for example—and the ions of another—iodide, in this case. The iodide ions are dissolved from a salt such as sodium iodide or potassium iodide. The sodium or potassium ions are spectator ions and therefore irrelevant to the reaction, which proceeds as follows:
\[Cl_2 + 2I^- \rightarrow 2Cl^- + I_2\]
- The iodide ions lose electrons to form iodine molecules; they are oxidized.
- The chlorine molecules gain electrons to form chloride ions. They are reduced.
This is a redox reaction in which chlorine is acting as an oxidizing agent. The driving force force this reaction is straightforward to identify from the table of Standard Reduction Potentials (Table P2).
Contributors and Attributions
- Jim Clark (ChemGuide)