Frost diagram
Frost diagrams (also frost diagrams) are a graphical representation of the reduction potentials of half-reactions - for each of the different oxidation states of the element. They were introduced by Arthur A. Frost in 1950 as an alternative to Latimer diagrams. It is a Cartesian coordinate system is used, in which the abscissa is the oxidation number, and the ordinate values usually the half-reaction oxidation state of the oxidation state 0 (eg ). The value is directly proportional to the free energy by:
There are also frost - free graphs for which enthalpies instead of the value are plotted. The potential data may refer to standard conditions () or to any other specified conditions (eg: ).
Draw up
Diagram for vanadium in acidic solution ():
1) are taken from the standard potentials of the relevant redox equilibria of a table works:
2 ) It is determined that n · E- values:
3) The values are entered in a coordinate system.
Interpretation
The diagram shows information about special redox processes can be obtained as soon as an oxidation stage is on an extreme value. A connection is in the Frost diagram on a maximum, the decay is in the two stages left and right ( disproportionation ) very likely. However, there is a link to a minimum, the reaction of the two adjacent links to this same oxidation ( comproportionation ) is very likely. A disproportionation occurs when responding to dithionate, sulfate and sulfite (or sulfur trioxide and sulfur dioxide in aqueous solution). Exemplary of the comproportionation reaction of and (see Example diagram).