Extraction & REDOX

• Metal + Oxygen -> Metal Oxide

  • Most metals are found as METAL OXIDES in the environment in rocks called ORES.
  • So they require chemical reactions to extract the PURE METAL from it.
• OXIDATION:


  When metals react with Oxygen, they form metal oxides.

  • It's a chemical process involving the:
  • GAIN OF OXYGEN
  • LOSS OF ELECTRONS

  Example; where oxygen is gained by copper:

  • Copper + Oxygen -> Copper Oxide
  • 2Cu + O2 -> 2CuO
• Reduction:


  The process of EXTRACTING a metal from its oxide.

  • It's a reaction involving the:
  • LOSS OF OXYGEN
  • GAIN OF ELECTRONS

  E.g. where oxygen is lost by copper oxide:

  • Copper Oxide + Carbon -> Copper + Carbon Dioxide
  • 2CuO + C -> 2Cu + CO2
• EXTRACTION TECHNIQUES of getting METALS from the Earth, that is based on the metal's position in the reactivity series:

  • No extraction
  • Reduction with Carbon
  • Electrolysis

  
• No Extraction:


  Metals that are UNREACTIVE like GOLD can be found on Earth as itself, so NO extraction is required.

  • It can simply be collected.
• Reduction with Carbon:


  Used to extract Metals LESS reactive than CARBON.

  • As carbon will be MORE REACTIVE than the metal, so it will remove the oxygen from the metal and form Carbon Dioxide.

  E.g. copper ore reacts with carbon to give copper & carbon dioxide:

  • Copper Oxide + Carbon -> Copper + Carbon Dioxide
  • 2CuO + C -> 2Cu + CO2
• Electrolysis


  Used by Metals MORE reactive than CARBON.

  • It's a MORE EXPENSIVE method due to the cost of electricity and requires lots of energy.
• we find pure gold in the ground, but not pure iron:

  • Gold is unreactive, so doesn't react with any other elements
  • Iron is reactive enough to react with oxygen, so is oxidised to iron oxide 
• REDOX


  Stands for reduction-oxidation.

  • It is when reduction AND oxidation occur in the same reaction.
  • These reactions are all about the transfer of ELECTRONS between substances:
  • OXIDATION is where a substance LOSES electrons and gain of oxygen.
  • REDUCTION is where a substance GAINS electrons and lose of oxygen.
• OIL RIG


  Oxidation

  Is

  Loss

  • this is what happens to electrons during redox reactions

  Reduction

  Is

  Gain
• Displacement Reactions:

  examples of REDOX REACTIONS:

  • This occurs when a  MORE REACTIVE METAL replaces a LESS reactive METAL in a compound.
• E.g. Zinc is placed in a Copper Sulfate solution:

  • Zinc is HIGHER in the reactivity series, so it REPLACES copper to form ZINC SULFATE.
  • Zn + CuSO4 -> ZnSO4 + Cu
  • $Zn\:+$$\:Cu^{2+}+$$SO^{2-}4\:->\:Zn^{2+}+$$\:SO^{2-}4\:+$$Cu$

  The element Zn turns into Zn2+

  • Zinc LOST TWO ELECTRONS , to get a charge of +2
  • Zinc has been OXIDISED

  The ion Cu2+ turns into Cu:

  • Cu2+ GAINED two electrons
  • Copper has been REDUCED
• Half Equations


  shows the ELECTRON TRANSFERS within an ionic equation.

  Electrons in half equations are represented as an e-.

  • The REDUCTION half equation:
  • Shows the element that GAINS electrons.
  • Electrons here are written on the REACTANTS side
  • (left hand side).
  • The OXIDATION half equation:
  • Shows the element that LOSES electrons.
  • Electrons here are written on the PRODUCTS side
  • (right hand side).

  
• Mining for iron

  • When we take Rocks from the ground and separate out the bits that contain iron
  • There's lots of different iron ores - referring to metal rich compounds that we can extract out metal from.
  • The most common ore is Fe2O3, (a type of iron oxide) so to isolate the pure iron, we need to reduce this iron oxide to just iron.

  Iron III oxide + carbon -> carbon dioxide + Iron

  • $2Fe_2O_3\:+$$3C\:\:->\:3CO_2\:+$$\:4Fe$

  Fe2O3 has been reduced to Fe by losing its oxygen.

  • Carbon has been Oxidized to Carbon dioxide by gaining oxygen from Fe2O3.

  
• REDOX reactions don't happen by themselves, both takes place at the same time:


  • Magnesium atoms would lose two electrons and be oxidized - forming magnesium 2+ ions.

  while the hydrogen ions will gain those electrons and be reduced to neutral hydrogen atoms in the form of hydrogen gas

  • Magnesium + Dilute Acid -> Oxidised magnesium + Hydrogen gas
  • $Mg+$$2H^+$$->\:Mg^{2+}+$$H_2$
• Malachite - green


  Copper Carbonate (CuCO3)

  
• Hematite - purple


  Iron Oxide (Fe2O3)

  
• Bauxite - orange


  Aluminium Oxide (Al2O3)

  
• Fe + O -> Fe2O3 (rust)
• As oxygen is mostly in our atmosphere, most of the metal on earth will have come into contact with it as some point.

  • There's also elements bonded to other elements as well, but oxygen is the common.

  
• Oxidation:


  Ca  ➔  Ca2+  +  2e-
• Sodium reacts with iron sulphate.

  • Fe2+ + 2e-  ➔ Fe
  • Na  ➔  Na+  +  e-
• Spectator ion:

  An ion that doesn't take part in the reaction & so keeps the same charge. 
• 2K  +  CuCl2  ➔  2KCl  +  Cu

  • The Cl- ion doesn't take part, so it's a Cl- ion on both sides.
  • Chloride is the spectator ion.