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Time dependent excess concentration
Posted 11.09.2015, 04:48 GMT-4 Chemical Reaction Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.0 1 Reply
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Hello
Could anyone please explain me the physical concept of excess concentration (for example for anions)??
I was able to only model the ion concentration at boundaries or domains but what is the concept of excess concentration?
Regards
Could anyone please explain me the physical concept of excess concentration (for example for anions)??
I was able to only model the ion concentration at boundaries or domains but what is the concept of excess concentration?
Regards
1 Reply Last Post 11.09.2015, 07:41 GMT-4
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Posted:
9 years ago
Hi
In terms of adsorption, excess concentration is defined as the deviation from the bulk concentration with respect to the concentration of the solvent, usually water. Look any physical chemistry textbook and "surface excess".
What comes to ion excess, there is none in the bulk of the solution due to electroneutrality. Only close to a charged surface (like an electrode) there is a deficit of like charges and excess of opposite charges. This region extends only a few Å into the solution. But this is what you have apparently already calculated.
Unlike excess enthalpy or entropy, excess concentration is not - at least to my knowledge - any generally accepted concept.
Lasse
In terms of adsorption, excess concentration is defined as the deviation from the bulk concentration with respect to the concentration of the solvent, usually water. Look any physical chemistry textbook and "surface excess".
What comes to ion excess, there is none in the bulk of the solution due to electroneutrality. Only close to a charged surface (like an electrode) there is a deficit of like charges and excess of opposite charges. This region extends only a few Å into the solution. But this is what you have apparently already calculated.
Unlike excess enthalpy or entropy, excess concentration is not - at least to my knowledge - any generally accepted concept.
Lasse