Chemical changes

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5.1 The reactivity series

  • Ores are rocks from which it's economical to extract the metals that they contain 
  • To extract metals from their oxides, you must reduce it
  • The reactivity series is a list of elements in order of reactivity, with most reactive at the top and least reactive at the bottom

Metals plus water

  • Most metals don't react vigorously w/ water
  • Metals, e.g. copper can be used to make water pipes
  • Alkali metals react w/ water and give off hydrogen and leave alkaline solutions

Metals plus dilute acid

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5.2 Displacement reactions - redox reactions

  • A more reactive metal will displace a less reactive metal from an aqueous solution of 1 of its salts
  • Mg is more reactive than Cu so Cu ions will be displaced from a solution to from Cu metals and aqueous Mg ions which dissolves in the soloution - displacement reaction
  • An ionic equation shows only the atoms and ions that change in a reaction, e.g. Carbon can be used to extract metals from their oxides as long as the metal's below Al
    • Mg (s) + Cu^2+ (aq) --> Mg^2+ (aq) + Cu (s)
  • Oxidation         (chemical addition of O2)
  • Is
  • Loss of electrons
  • Reduction        (chemical removal of O2)
  • Is
  • Gain of electrons

5.3 Extracting metals

  • Metals are found in the Earth's crust and are often combined w/ oxygen or sulfur
  • A metal ore contains enough of the metal to make it economic to extract the metal. Ores are mined and might need to be concentrated before the metal's extracted and purified
  • Copper is ground into powder and then mixed w/ water and a chemical to make the copper repel water. Air's then bubbled through the mixture and the copper floats to the top as a froth. The rocky bits sink and the conc. copper is scraped off the top - ready to be extracted
  • Whether it's worth extracting depends on:Gold and some unreactive metals can be found in their natural state
    • how easy it is to extract from its ore
    • how much metal the ore contains
    • the changing demands for a certain metal
  • Carbon displaces less reactive metals from their oxides and is used to extract metals from their ores
  • Heat carbon w/ the metal oxide so it can remove O2 from the metal oxide to make CO2
    • metal oxide + carbon --> metal + carbon dioxide
  • Tungsten, W, can be extracted by reduction using hydrogen. Hydrogen's used because carbon froms a compound w/ the metal formed by reductionElements more reactive than carbon are extracted by electrolysis of the molten metal compound
    • tungsten oxide + hydrogen --> tungsten + water

5.4 Salts from metals

  • Salts and hydrogen are made by reacting metals (above hydrogen

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