gcse science chemistry unit C6 part 1

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  • Created by: charlie
  • Created on: 07-05-13 21:03
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  • C6
    • fuel cells
      • fuel + O2 makes energy
      • hydrogen oxygen fuel cell
        • redox reaction
        • efficiency 80% and direct energy
        • producing H2 needs power and H2 contains poisonous catalyst- money to get rid of
        • in spacecraft
          • electricity
          • lightweight and waste water reused
        • in car industry
          • only heat and water produced
          • hydrogen made by decomposing water (electrolysis)
    • rusting  of Fe
      • redox
      • iron + oxygen +water = hydrated iron (III) oxide
      • stopping rusting
        • oil and grease paint
          • physical barrier
        • tin
          • physical barrier  but less reactive
        • iron + more reactive metal
          • sacrificial metal  Zn Mg
        • alloys
          • stainless steel
    • redox reactions
      • OIL RIG
      • both oxidation and reduction happen at same time
      • displacement reactions
      • Fe - 2e' = Fe2+
        • 2H+ + 2e' = H2
          • oxidising agent
        • reducing agent
    • CFC's and ozone layer
      • first- good, non toxic, non flammable, inert
        • 1974- Cl destroys O3
          • 1978-  banned USA, Canada, Sweden
            • 1985- hole over Antarctica  and every country reduced use
      • 1)  CCL2F2 = CCLF2 + Cl.
        • 2)  O3 + Cl. = CLO. +O2
      • free radicals
        • covalent bond breaks even and each atom shares e'
        • CFC's stay around one molecule reacts with thousands of O3
      • refrigerants and propellants
      • breakdown
        • O3+UV=O+O2
          • O+O2=O3
      • alternatives
        • alkanes
          • dont react with O3
        • HFC's
          • no chlorine
    • electrolysis
      • splitting up with electricity
      • H2SO4 (aq)
        • H2 ions
          • +ve
            • ions go to cathode gain e'
            • 2H+ +2E'=H2
        • OH' ions
          • -ve
            • ions go to anode lose e'
            • 4OH' - 4e'=O2+2H2O
      • electrons transferred
        • increases with time
        • increases with current
          • Q=IT(s)
            • increases with time

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