3. If Fe is left outside it will eventually rust. What causes this redox reaction? Fe changes into Fe 2+ and O 2 changes into OH 1-. Write 2 balanced half reactions to show these oxidation reduction reactions. FeFe 2+ +2e 1- O2O2 OH 1- + H 2 O3H 1+ +4e 1- + 224 2Fe + 3H 1+ + O 2 2Fe 2+ + OH 1- + H 2 O +3OH 1- 2Fe + 3H 2 O + O 2 2Fe 2+ + 4OH 1- + H 2 O - H 2 O 2Fe + 2H 2 O + O 2 2Fe 2+ + 4OH 1-

4. Fe H2OH2O

5. 2Fe O2O2 2Fe + 2H 2 O + O 2 2Fe 2+ + 4OH 1- 2Fe 2+ O 2 + 2H 2 O + 4e 1- 4OH 1- 2Fe2Fe 2+ + 4e 1- 4e 1- 4OH 1-

6. 2Fe O2O2 2Fe + 2H 2 O + O 2 2Fe 2+ + 4OH 1- 2Fe 2+ O 2 + 2H 2 O + 4e 1- 4OH 1- 2Fe2Fe 2+ + 4e 1- 4e 1- 4OH 1- Over time the Fe(OH) 2 accumulates as a solid due to low solubility and is further oxidized by H 2 O and O 2 into Fe(OH) 3

7. 2Fe O2O2 2Fe 2+ 4e 1- 4OH 1- Over time the Fe(OH) 2 accumulates as a solid due to low solubility and is further oxidized by H 2 O and O 2 into Fe(OH) 3 Write a balanced equation showing the formation of ferric hydroxide from ferrous hydroxide, water and oxygen.

8. 2Fe O2O2 2Fe 2+ 4e 1- 4OH 1- Write a balanced equation showing the formation of ferric hydroxide from ferrous hydroxide, water and oxygen using the oxidation number method. Fe(OH) 2 + O 2 + H 2 OFe(OH) 3 2+3+02- 1e 1- /Fe 1e 1- /Fe(OH) 2 2e 1- /O 4e 1- /O 2 4 4 Balance O using water 2

9. 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.

10. underground Fe tank Mg Fe 2+ + 2e 1-  Fe- 0.45 V Mg 2+ + 2e 1-  Mg - 2.37 V Mg  Mg 2+ + 2e 1- - 2.37 V Fe 2+ + Mg  Mg 2+ + Fe1.92 V e 1-

11. underground Fe tank Mg Fe 2+ + 2e 1-  Fe- 0.45 V Mg 2+ + 2e 1-  Mg - 2.37 V Mg  Mg 2+ + 2e 1- - 2.37 V Fe 2+ + Mg  Mg 2+ + Fe1.92 V e 1-

12. underground Fe tank Mg Fe 2+ + 2e 1-  Fe- 0.45 V Mg 2+ + 2e 1-  Mg - 2.37 V Mg  Mg 2+ + 2e 1- - 2.37 V Fe 2+ + Mg  Mg 2+ + Fe1.92 V e 1-

13. underground Fe tank Mg Fe 2+ + 2e 1-  Fe- 0.45 V Mg 2+ + 2e 1-  Mg - 2.37 V Mg  Mg 2+ + 2e 1- - 2.37 V Fe 2+ + Mg  Mg 2+ + Fe1.92 V e 1-

14. underground Fe tank Mg Fe 2+ + 2e 1-  Fe- 0.45 V Mg 2+ + 2e 1-  Mg - 2.37 V Mg  Mg 2+ + 2e 1- - 2.37 V Fe 2+ + Mg  Mg 2+ + Fe1.92 V e 1-

15. underground Fe tank Mg Fe 2+ + 2e 1-  Fe- 0.45 V Mg 2+ + 2e 1-  Mg - 2.37 V Mg  Mg 2+ + 2e 1- - 2.37 V Fe 2+ + Mg  Mg 2+ + Fe1.92 V e 1-