Which species of Fe are considered dissolved Fe?

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Discussion Overview

The discussion revolves around the classification of dissolved iron species, specifically whether Fe(OH)42- is considered a dissolved species of iron and the implications of its activity in solution. Participants explore the assumptions related to the activity of iron species in the context of drawing an Eh-Ph diagram.

Discussion Character

  • Homework-related, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether Fe(OH)42- is considered a dissolved species of iron, expressing uncertainty about its classification despite it being an ion.
  • Another participant challenges the assertion that all dissolved iron species have an activity of 0.1M, requesting the full context of the question.
  • A later reply suggests that the 0.1M activity is an assumption for simplification in drawing an Eh-Ph diagram, rather than a universally applicable statement.
  • One participant notes that water solutions containing iron ions involve multiple equilibria and that the activity of the main form can be assumed to be 0.1M, but this does not apply to all forms present.
  • A participant mentions consulting their professor, who clarified that Fe(OH)42- does not have an activity of 0.1M, indicating a divergence in understanding.

Areas of Agreement / Disagreement

Participants express differing views on the classification of dissolved iron species and the validity of the 0.1M activity assumption, indicating that multiple competing views remain and the discussion is unresolved.

Contextual Notes

Limitations include the lack of context for the original question, which may affect the interpretation of the activity of iron species and the assumptions made regarding their classification.

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Homework Statement


The question tells me that all dissolved iron species will have an activity of 0.1M. So is Fe(OH)42- considered a dissolved species of Fe, and if so, it will have an activity of 0.1M?

Homework Equations



N/A

The Attempt at a Solution



I want to say that it is not considered as such, but the fact that it is an ion troubles me.
 
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1question said:
The question tells me that all dissolved iron species will have an activity of 0.1M.

Doesn't sound correct to me, can you post entire question?
 
It's an assumption so that I can draw a simplified Eh-Ph diagram. It is not meant to be generally correct I believe.
 
Every water solution containing iron ions will also have many equilibria present, with numerous products of Fe(II) and Fe(III) reactions with water. You can assume activity of the main (dominating) form present in the solution to be 0.1 M, or you can assume sum of all forms present to be 0.1 M (it will be just a mass balance then), but in neither case activities of other forms will be 0.1 M.

Chances are this is just a lousy wording and there is a viable idea behind the statement, but without the context I can't see it.
 
I asked my Prof. It does not have an activity of 0.1M. Thanks for your help Borek.
 

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