If Fe is left outside it will eventually rust.What causes this redox reaction?Fe changes into Fe2+ and O2 changes into OH1-.Write 2 balanced half reactions to show these oxidation reduction reactions.

Fe Fe2+ + 2e1-

O2 OH1- + H2O3H1+ +4e1- +2 2 4

2Fe + 3H1+ + O2 2Fe2+ + OH1- + H2O+3OH1- +3OH1-

2Fe + 3H2O + O2 2Fe2+ + 4OH1- + H2O- H2O - H2O

2Fe + 2H2O + O2 2Fe2+ + 4OH1-

Fe

H2O

2Fe

O2

2Fe + 2H2O + O2 2Fe2+ + 4OH1-

2Fe2+

O2 + 2H2O + 4e1- 4OH1-

2Fe 2Fe2+ + 4e1-

4e1-4OH1-

2Fe

O2

2Fe + 2H2O + O2 2Fe2+ + 4OH1-

2Fe2+

O2 + 2H2O + 4e1- 4OH1-

2Fe 2Fe2+ + 4e1-

4e1-4OH1-

Over time the Fe(OH)2 accumulates as a solid due to low solubility and is further oxidized by H2O and O2 into Fe(OH)3

2Fe

O22Fe2+

4e1-4OH1-

Over time the Fe(OH)2 accumulates as a solid due to low solubility and is further oxidized by H2O and O2 into Fe(OH)3

Write a balanced equation showing the formation of ferric hydroxide from ferrous hydroxide, water and oxygen.

2Fe

O22Fe2+

4e1-4OH1-

Write a balanced equation showing the formation of ferric hydroxide from ferrous hydroxide, water and oxygen using the oxidation number method.

Fe(OH)2 + O2 + H2O Fe(OH)3

2+ 3+0 2-

1e1-/Fe1e1-/Fe(OH)2

2e1-/O4e1-/O2

4 4

Balance O usingwater

2

If Fe objects are buried under ground where there is water with dissolved oxygen in it how can they be protected from rusting?Hint: look at the Standard Reduction Table and find the reduction of iron.If another metal with a weaker pull on electrons is placed in contact with the iron it will be oxidized instead of the iron.Iron will be reduced when combined with a metal which is a weaker oxidizing agent.

underground Fe tank

Mg

Fe2+ + 2e1- Fe - 0.45 VMg2+ + 2e1- Mg - 2.37 VMg Mg2+ + 2e1- - 2.37 VFe2+ + Mg Mg2+ + Fe 1.92 V

e1-e1-e1-e1-e1-e1-e1-

underground Fe tank

Mg

Fe2+ + 2e1- Fe - 0.45 VMg2+ + 2e1- Mg - 2.37 VMg Mg2+ + 2e1- - 2.37 VFe2+ + Mg Mg2+ + Fe 1.92 V

e1-

underground Fe tank

Mg

Fe2+ + 2e1- Fe - 0.45 VMg2+ + 2e1- Mg - 2.37 VMg Mg2+ + 2e1- - 2.37 VFe2+ + Mg Mg2+ + Fe 1.92 V

e1-

underground Fe tank

Mg

Fe2+ + 2e1- Fe - 0.45 VMg2+ + 2e1- Mg - 2.37 VMg Mg2+ + 2e1- - 2.37 VFe2+ + Mg Mg2+ + Fe 1.92 V

e1-

underground Fe tank

Mg

Fe2+ + 2e1- Fe - 0.45 VMg2+ + 2e1- Mg - 2.37 VMg Mg2+ + 2e1- - 2.37 VFe2+ + Mg Mg2+ + Fe 1.92 V

e1-

underground Fe tank

Mg

Fe2+ + 2e1- Fe - 0.45 VMg2+ + 2e1- Mg - 2.37 VMg Mg2+ + 2e1- - 2.37 VFe2+ + Mg Mg2+ + Fe 1.92 V

e1-