Cell notation

Cell notation or line notation in chemistry is a shorthand way of expressing a certain reaction in an electrochemical cell. The cell anode and cathode (half-cells) are separated by two bars or slashes representing a salt bridge, with the anode on the left and cathode on the right.[1][2] Individual solid, liquid or aqueous phases within each half-cell are separated by a single bar. Concentrations of dissolved species, in each phase written in parentheses and the state of each phase (usually s (solid), l (liquid), g (gas) or aq. (aqueous solution)) is included in a subscript after the species name.

Some examples of this notation are:

Zn°|Zn2+||Cl−|AgCl|Ag°

This means that the left electrode (anode) is made of zinc, while the other one (right, cathode) is composed of a silver wire covered by a silver chloride layer which is not soluble. Both of the electrodes are immersed into aqueous media where zinc and chloride ions are present.[3]

Zn°|Zn2+, SO42−||SO42−,Cu2+|Cu°

This cell is very famous: the Daniell cell. If the electrodes are connected, a spontaneous reaction takes place. Zinc is oxidized, and copper ions are reduced.

Sometimes the state of each species into the cell is written. For example, in the zinc cell (shown above), we can write that zinc, silver and silver chloride are solids, while zinc cation and chloride anion are in aqueous medium. So, the new notation will be:

Zn°s|Zn2+aq || Cl−aq|AgCls|Ag°s

It is possible to express the ion concentration too. For example, in the Galvanic cell:

Zn°s|Zn2+aq (1 mol/L), SO42−aq (1 mol/L)||SO42−aq (1 mol/L)|Cu2+aq(1 mol/L)|Cu°s

In this case, all ions (sulfate, zinc and copper) are in a concentration equal to 1 mol/L.

References
  1. Wiley Interscience
  2. http://www.sparknotes.com/chemistry/electrochemistry/galvanic/section2.rhtml
  3. Bard, A. J. and Faulkner, L. R. "Electrochemical methods. Fundamentals and applications", John Whiley & Sons, Inc, 2nd edition, USA, 2001


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.