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Unit 2 B Notes Metal Uses Redox 08 09

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Unit 2 B Notes Metal Uses Redox 08 09

  1. 1. Unit 2B Earth’s Mineral Resources
  2. 2. Metal Uses <ul><li>Humans – toolmakers </li></ul><ul><ul><li>Stone Age </li></ul></ul><ul><ul><li>stone and copper tools first made 10,000 yrs ago </li></ul></ul><ul><ul><li>Unreactive native metals used to make coins, decorative objects, some tools (esp. Cu) </li></ul></ul>
  3. 3. Metal Uses <ul><ul><li>Bronze Age began 3800 BC </li></ul></ul><ul><ul><li>alloy of tin and copper </li></ul></ul>
  4. 4. Metal Uses <ul><ul><li>Iron Age began 1000 BC </li></ul></ul><ul><ul><ul><li>man discovered fire can be used to separate iron from iron ore </li></ul></ul></ul><ul><ul><ul><li>Additional metals removed from ores </li></ul></ul></ul>
  5. 6. Worthwhile to mine a metal? <ul><li>Consider </li></ul><ul><li>amt of useful ore at the site </li></ul><ul><li>% of metal in the ore </li></ul><ul><li>type of mining and processing needed to extract the metal from its ore </li></ul>
  6. 7. Worthwhile to mine a metal? <ul><li>distance of mine from metal refining facility and markets </li></ul><ul><li>metal’s supply-vs-demand </li></ul>
  7. 10. Metal Reactivity <ul><li>How readily a certain metal reacts with oxygen provides information about the metal’s reactivity. </li></ul><ul><li>If elements are ranked in relative order of their chemical reactivity, the ranking is called an activity series . </li></ul>
  8. 11. Metal Reactivity <ul><li>If copper is heated in air, it will react w/ oxygen to produce a black substance: </li></ul><ul><li>2 Cu(s) + O 2 (g) 2 CuO(s) </li></ul><ul><li>Copper + Oxygen Copper(II) oxide </li></ul>
  9. 12. Metal Reactivity <ul><li>However, magnesium will react w/ oxygen when heated by igniting and releasing brilliant light: </li></ul><ul><li>2 Mg(s) + O 2 (g) 2 MgO(s) </li></ul><ul><li>Magnesium + Oxygen Magnesium oxide </li></ul>
  10. 13. Metal Reactivity <ul><li>Gold does not react with oxygen (even at high T) </li></ul><ul><li>Durable, long-lasting </li></ul><ul><li>Suitable for use in jewelry, electronics </li></ul>
  11. 14. Metal Reactivity <ul><li>most reactive metallic elements are at the top ; </li></ul><ul><li>less reactive elements are closer to the bottom . </li></ul>
  12. 15. Refining Metals <ul><li>Metal reactivity generally decreases from left – right on periodic table </li></ul><ul><li>If Metal X is listed above Metal Y in an activity series, then Metal X will react (reduce) with Metal Y in solution </li></ul>
  13. 16. Refining Metals <ul><li>Ores generally contain metals in ionic form (cations), these cations need to be combined with electrons in a chemical reaction to obtain useful neutral metal atoms </li></ul>
  14. 17. Refining Metals <ul><li>Reduction reactions – any chemical change in which a cation gains electrons </li></ul><ul><li>Cu 2+ + 2e - Cu (metal) </li></ul><ul><li>Oxidation reactions – any reaction in which atoms lose electrons </li></ul><ul><li>Cu (metal) Cu 2+ + 2e - </li></ul>
  15. 18. Refining Metals <ul><li>To gain electrons, chemists must “supply” electrons from atoms that readily lose electrons </li></ul><ul><li>Oxidation and reduction reactions must occur simultaneously, therefore we group them together and call them Redox reactions </li></ul>
  16. 19. Refining Metals <ul><li>Cu (s) + 2Ag + (aq) Cu 2+ (aq) + Ag (s) </li></ul><ul><li>Copper was oxidized </li></ul><ul><ul><li>(converted to Cu 2+ by losing two electrons </li></ul></ul><ul><li>Each silver ion was reduced </li></ul><ul><ul><li>(converted to a silver atom by gaining one electron) </li></ul></ul>
  17. 20. <ul><li>Cu 2+ (aq) + Mg (s) Cu (s) + Mg 2+ (aq) </li></ul><ul><li>Magnesium atoms are oxidized </li></ul><ul><li>Copper ions are reduced </li></ul><ul><li>The reducing agent is Magnesium (source of electrons for the metal being obtained) </li></ul><ul><li>Total electrical charges and atoms must balance on each side of the reaction – Why? </li></ul>
  18. 21. Refining Metals <ul><li>LEO the lion goes GER </li></ul><ul><li>L oses E lectrons = O xidation </li></ul><ul><li>G ains E lectrons = R eduction </li></ul><ul><li>Obtaining metals from ores requires: </li></ul><ul><ul><li>energy and a reducing agent </li></ul></ul>
  19. 22. Refining Metals <ul><li>Electrometallurgy uses an electric current to serve as a reducing agent </li></ul><ul><ul><li>Used when pure metal is needed or no suitable aqueous reducing agent is available </li></ul></ul>
  20. 23. Refining Metals <ul><li>Pyrometallurgy uses heat (furnaces) or more reactive metals to reduce metal ores </li></ul><ul><ul><li>Oldest method, most widely used method </li></ul></ul>
  21. 24. Refining Metals <ul><li>Hydrometallurgy – reduction of metal ions from ores in aqueous solutions (leaching) </li></ul><ul><ul><li>May be used to obtain metals from old “tailings” (leftover rock from previous ore processing) </li></ul></ul>