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Rusting. Rusting and the redox cycle. Reduction. Extraction. Metal oxide Fe 3+. Metal Fe. Corrosion. Oxidation. Rusting is an electrochemical process. O 2. O 2. Fe 2 O 3 .xH 2 O (rust). +O 2 (aq). 2OH - +. Fe 2+. Fe(OH) 2. O 2. O 2. ½ O 2 + 2e - +H 2 O 2OH -. Fe 2+.
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Rusting and the redox cycle Reduction Extraction Metal oxide Fe3+ Metal Fe Corrosion Oxidation
Rusting is an electrochemical process O2 O2 Fe2O3.xH2O (rust) +O2(aq) 2OH- + Fe2+ Fe(OH)2 O2 O2 ½ O2 + 2e- +H2O 2OH- Fe2+ Fe e- e- Fe Fe2+ + 2e-
Fe2+ + 2e-Fe EΘ= -0.44V Oxidised Fe Fe2+ + 2e- Reduced ½ O2 +2e- + H2O 2OH- ½ O2 +2e- + H2O + Fe 2OH- + Fe2+ + 2e- Precipitation Fe2+ (aq)+ 2OH- (aq) Fe(OH)2 (s) Oxidised Fe(OH)2 (s) Fe2O3. x H2O (s) ½ O2 +2e- + H2O 2OH-EΘ= +0.40V