Types of Half Cells

A half cell is a structure that contains a conductive electrode and a surrounding conductive electrolyte separated by a naturally occurring Helmholtz double layer. There are three main types of half cells: metal-insoluble metal salt-anion electrodes, gas-ion electrodes, and ion-ion electrodes.

Questions

• What are the three main types of half cells?
• How is a metal-insoluble metal salt-anion electrode constructed?
• What is an example of a gas-ion electrode?
• What is an example of an ion-ion electrode?

Answers

• The three main types of half cells are metal-insoluble metal salt-anion electrodes, gas-ion electrodes, and ion-ion electrodes.
• A metal-insoluble metal salt-anion electrode is constructed with a metal with its insoluble metal salt dipped in a solution containing the common anion of the salt. For example, a rod of Ag coated with a paste of AgCl dipped in a solution of Cl- ions.
• An example of a gas-ion electrode is the H+/H2 electrode, which consists of a platinum electrode in contact with a solution of H+ ions and hydrogen gas.
• An example of an ion-ion electrode is the Fe3+/Fe2+ electrode, which consists of a platinum electrode in contact with solutions of Fe3+ and Fe2+ ions.