TOPIC 4

• Metal oxides

  Metals react with oxygen in the air to produce metal oxides
• Oxidation


  Reaction in which oxygen is added to an element or a compound
• Reduction

  Reaction in which oxygen is removed from an element or a compound
• Reaction of copper metal with oxygen

  • 2Cu + O2 → 2CuO
• In the reaction of copper metal with oxygen, copper metal has been oxidised since oxygen has been added to it
• Reaction of zinc oxide with carbon

  • ZnO + C → Zn + CO
• In the reaction of zinc oxide with carbon, the zinc oxide has been reduced since it has lost oxygen
• Reactivity series of metals

  Based on how they react with other substances, a series can be produced in which the metals are placed in order of their reactivity

  
• Tendency of a metal to lose electrons

  A measure of how reactive the metal is
• Hydrogen is placed in the reactivity series because metals only react with acid if the metal is more reactive than hydrogen
• Carbon is placed in the reactivity series because it allows us to see whether a metal oxide can be reduced by carbon or not for metal extraction
• Reactivity with water

  Some metals react with water, forming a metal hydroxide and hydrogen gas
• Reaction of calcium with water

  • Ca + 2H2O → Ca(OH)2 + H2
• Magnesium reaction with water

  Magnesium reacts very slowly with cold water when finely divided, but reacts with gaseous water to form a metal oxide and hydrogen gas

  
• Metals reacting with acids


  Most metals react with dilute acids, replacing the hydrogen atom in the acid with the metal atom to produce a salt and hydrogen gas
• Reaction of iron with hydrochloric acid

  • Fe + 2HCl → FeCl2 + H2
• Aluminium is high in the reactivity series, but it does not react with water and the reaction with dilute acids can be quite slow due to a protective oxide layer
• Non-metals like carbon and hydrogen appear in the reactivity series of metals because they play different roles in understanding metal reactions and extraction
• Carbon as a reducing agent

  Carbon can be used to remove oxygen from metal oxide ores, allowing extraction of metals below carbon in the reactivity series
• Extraction of metals above carbon

  Extracted using electrolysis
• Extraction of metals below carbon

  Extracted using carbon as a reducing agent
• Some metals like gold are unreactive and found as uncombined elements, known as native metals
• Displacement reactions


  A more reactive metal will displace a less reactive metal from its compounds
• Reduction of copper(II) oxide by heating with zinc


  • Zn + CuO → ZnO + Cu
• Displacement reactions between metals and aqueous solutions

  The more reactive metal slowly disappears from the solution, displacing the less reactive metal