please answer the following question 1- Assuming a bicarbonate ion concentration
ID: 941113 • Letter: P
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please answer the following question
1- Assuming a bicarbonate ion concentration [HCO3 - ] 0f 1.00 x 10-3 M and a value of 3.5 x 10-11 for the solubility product constant of FeCO3, what would you expect to be the stable iron species at pH 9.5 and pE -8.0. Use the pH-pE diagram as uploded in the picture:
nidation-Reduction in Aquatic Chemistry Oxi 95 20 15 10 02 pE Fe2+ Fe(OH)3 -10 H2 0 12 3 4 5 67 8 9 10 1 12 13 14 pH 44 Simplified pE-pH diagram for iron in water. The maximum soluble iron concentration is .00x 10-5 M FGURE 44 SimplifiExplanation / Answer
The equilibrium composition of a redox system involving H+ depends on both the pH and the pE.
The interplay of these two factors is best illustrated by constructing a phase diagram in which the various lines represent states of (pE,pH) at which equilibria occur.
Diagrams of this kind are widely employed in geochemistry, oceanographic chemistry and in corrosion engineering.
States not falling on lines correspond to the predominance of a single species. Horizontal lines correspond to redox couples in which protons are not involved, while vertical lines represent acid-base reactions without electron transfer.
In establishing a line separating a solid from a dissolved species, it is necessary to define the equilibrium concentration at which the dissolved species is so low that is is considered to be the unstable form.
This concentration is of course entirely arbitrary, and is selected according to the application one has in mind. A value of 107 M is used in the diagram for the Fe3+–Fe2+ system in Figure.
The stable ions can be calculated by the formula :
pE = F/ 2.3RT E
The horizontal axis is labeled pH for the -log function of the H+ ion activity.
Eh = 1.229V - 0.0591* pH (V)
pE = Eh / 0.0591V
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