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Eh represents the oxidation-reduction potential based on the standard hydrogen potential (SHE), while pH represents the activity of the hydrogen ion (H+, also known as a proton). An Eh-pH diagram can describe not only the effects of potential and pH, but also of complexes, temperature and pressures.
What is depicted in EH-pH diagram?
Eh–pH diagram, any of a class of diagrams that illustrate the fields of stability of mineral or chemical species in terms of the activity of hydrogen ions (pH) and the activity of electrons (Eh). In natural environments, pH values extend from 1 to 9.5, and Eh values from -500 to +800 millivolts.
What is pE and pH?
In electrochemistry, and more generally in solution chemistry, a Pourbaix diagram, also known as a potential/pH diagram, EH–pH diagram or a pE/pH diagram, is a plot of possible thermodynamically stable phases (i.e., at chemical equilibrium) of an aqueous electrochemical system.
What is a pH diagram?
A p-h diagram is a figure with a vertical axis of absolute pressure and a horizontal axis of specific enthalpy. It is an important diagram used frequently for a performance calculation of a refrigerating machine. A p-h diagram is made respectively for a specified refrigerant.
What is eh measured in?
volts
Eh is a measurement of electrical potential and thus commonly expressed in volts. Values of Eh in nature range from -0.6 to +0.9V, with 0.0 characterizing a solution with no drive to either oxidize or reduce.
What is the difference between EH and pE?
The pE provides a nondimensional scale (like pH) that expresses the activity of electrons in factors of 10. Eh (called the redox potential) is measured in volts. F is the Faraday which is the electric charge of one mole of electrons (96,500 coulombs).
What does EH mean in chemistry?
Oxidation/Reduction Potential
Oxidation/Reduction Potential (Eh) Metal ions have strong and weak oxidizing/reducing potential. In order to evaluate redox reactions, the redox potential of a solution is measured and reported as Eh.
What is the significance of a line separating two species on an EH pH diagram?
The lines in the Pourbaix diagram show the equilibrium conditions, that is, where the activities are equal, for the species on each side of that line. On either side of the line, one form of the species will instead be said to be predominant.
What does a Pourbaix diagram tell you?
A Pourbaix diagram is a plot of the equilibrium potential of electrochemical reactions against pH. It shows how corrosion mechanisms can be examined as a function of factors such as pH, temperature and the concentrations of reacting species.
What are characteristics of Pourbaix diagram?
Characteristics of Pourbaix diagram: Horizontal lines represent electron transfer reactions. They are pH-independent, but potential-dependent. Vertical lines are potential-independent but pH-dependent and not accompanied by any electron transfer.