CI'III IT No Spati... Heading 1 Heading 2 J _______ Styli E: 'J Submission date: 2018 March 17 Show all calculaons, formulas and drawings clearly

Considering the following reactions and boundary conditions, construct a pe-pH speciation diagram for the iron system consisting of Fe(s)- Fe2+ - Fe(OH)2(s) - Fe3+ - Fe(OH)3 in freshwater. Use 1.0 x 10-5 M as the maximum soluble [Fe2+] or [Fe3+].

Given:

Reactions:

Fe3+ + e- ==== Fe2+ Fe2+ + 2 e- ===Fe(s)

Fe(OH)3(s) + 3H++ e- ==== Fe2+ + 3H2O

Fe(OH)3(s) + H++ e-=== Fe(OH)2(s) + H2O

Fe(OH)2(s) + 2 H+ + 2 e- ==== Fe(s) + 2 H20

Fe(OH)3(s) + 3 H+ ==== Fe3+ 3 H2O

Fe(OH)2(s) + 2 H+ ==== Fe2+ + 2H2O

Thermodynamic Data for Fe(s)- Fe2+ - Fe(OH)2(s)- Fe3- Fe(OH)3 system:

Ksp (Fe(OH)2) = 4.8 X 10-17

Ksp (Fe(OH)3) = 1.0 X 10-38

Standard Free Energy of Formation (∆G0f) in kJ/mol

(aq)H+

(aq)OH-

(aq)H2O(l)H30+(aq)Fe(s)

Fe2+(aq)

Fe3+ (aq)Fe(OH)2 (s)Fe(OH)3(s)

00-157.3-237.2-237.20-78.9-4.60-486.6-699

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