Frost diagram

Frost diagram

A Frost diagram is an Oxidation State Free Energy Diagram (O.S.F.E), also known as an Eh-pH diagram, due to its axial labellings, and is used in electrochemistry to illustrate the relative stability of a number of different oxidation states of a particular substance. Frost diagrams will be different at different pHs so the pH must be specified.

The pH dependence is given by the factor -0.059m/n per pH unit, where m relates to the number of protons in the equation, and n the number of electrons exchanged. Electrons are always exchanged in electrochemistry, but not necessarily protons. If there is no proton exchange in the reaction equilibrium, the reaction is said to be "pH independent". This means that the values for the electrochemical potential rendered in a redox half-reaction whereby the element/s in question change/s oxidation state are the same whatever the pH conditions under which the procedure is carried out.

On a Frost diagram the element is generally set as the reference point at 0 Volts.

The lower a point is on the Frost Diagram, the more stable it is. This indicates the most stable oxidation state for that element.Points found high in the upper left indicate an element that will act as a strong oxidizing agent at that oxidation state [http://www.wou.edu/las/physci/ch462/redox.htm] .

The gradient of the line between any two points on a Frost Diagram give the potential for the reaction. A species which lies in a peak, above the gradient of the two points on either side, denotes a species unstable with respect to disproportionation, and a point which falls below the gradient of the line joining its two adjacent points lies in a thermodynamic sink, and is "intrinsically stable".

The axes of the Frost diagram show (horizontally) the oxidation state of the species in question and (vertically) the electron exchange number multiplied by the voltage (nE) OR the Gibbs free energy per unit of the Faraday constant, ΔG/F.

An example of a Frost diagram: [http://facstaff.unca.edu/gheard/chem328/notes/V_frost.gif]


Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Pourbaix diagram — In chemistry, a Pourbaix diagram, also known as a potential/pH diagram, maps out possible stable (equilibrium) phases of an aqueous electrochemical system. Predominant ion boundaries are represented by lines. As such a Pourbaix diagram can be… …   Wikipedia

  • Comproportionation — Symproportionation or comproportionation is a chemical reaction where two reactants, each containing the same element but with a different oxidation number, will form a product with an oxidation number intermediate of the two reactants. For… …   Wikipedia

  • Electrochemistry — is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between… …   Wikipedia

  • climate — /kluy mit/, n. 1. the composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years. 2. a region or… …   Universalium

  • Curve sketching — In geometry, curve sketching (or curve tracing) includes techniques that can used to produce a rough idea of overall shape of a plane curve given its equation without computing the large numbers of points required for a detailed plot. It is an… …   Wikipedia

  • Runway — This article is about the aircraft take off and landing area. For other uses, see Runway (disambiguation). Landing strip redirects here. For the pubic hairstyle, see Bikini waxing. RWY redirects here. For the audio/video connectors, see RCA… …   Wikipedia

  • Formation and evolution of the Solar System — Artist s conception of a protoplanetary disk The formation and evolution of the Solar System is estimated to have begun 4.568 billion years ago with the gravitational collapse of a small part of a giant molecular cloud …   Wikipedia

  • Carbon dioxide clathrate — Carbon dioxide hydrate is a Type I gas clathrate (Sloan 1998). However, there has been some experimental evidence for the development of a metastable Type II phase at temperature near the ice melting point (Fleyfel and Devlin 1990, Staykova et al …   Wikipedia

  • List of meteorology topics — This is a list of meteorology topics. The terms relate to meteorology, the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting. (see also: List of meteorological phenomena)AlphanumericTOC… …   Wikipedia

  • Ice — This article is about water ice. For the broader concept of ices as used in the planetary sciences, see volatiles. For other uses, see Ice (disambiguation) …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”