Chemical Changes

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    Created by
    Hafsa Farouk

    Cards (8)

    • Reactivity: the tendency of a metal to form positive ions
      Ore: a type of rock that contains metal ions
      Species: a molecule or element within a chemical reaction/equation
    • metal + oxygen → metal oxide
      metal + water → metal hydroxide + hydrogen
    • • Metals higher than carbon in the reactivity series are extracted using electrolysis – very expensive
      • Metals below carbon are extracted by reduction using carbon e.g. iron oxide is reduced in a blast furnace
      o This is because carbon can displace a metal from its oxide when a metal is less reactive than carbon
    • REDuction & OXidation occur at the same time – called REDOX
    • • strong acids e.g. hydrochloric, nitric & sulfuric acids
      o completely ionised in aqueous solution
      ▪ all acid particles disassociate to release H+
      ions
      • weak acids e.g. ethanoic, citric & carbonic acids
      o only partially ionised in aqueous solution
      ▪ only a small proportions of acid particles disassociate to release H+
      ions
      o ionisation of a weak acid is a reversible reaction
      ▪ leads to an equilibrium of undissociated and dissociated acid
      ▪ since only a few acid particles release H+
      ions the position of equilibrium lies to the left
    • electrolytes - liquids & solutions are able to conduct electricity (must be ionic compounds)
      electrodes - solids that conduct electricity & are submerged in the electrolyte
    • o Aluminium oxide is extracted from bauxite ore
      o Aluminium oxide has a very high melting point, so adding cryolite reduces the melting point
      ▪ Cryolite is an aluminium based compound with a lower melting point than aluminium oxide
      • Positive Al3+ ions are attracted to the negative electrode (cathode)
      o they gain 3 electrons to form aluminium atoms which sink to the bottom of the electrolysis tank
      • Negative O2- ions are attracted to the positive electrode (anode)
      o they lose 2 electrons to form oxygen atoms which bond to form O2 molecules which are released
    • Aqueous solutions:
      o At the negative electrode (cathode) – H+ ions & positive metal ions are present
      ▪ If the metal is more reactive than hydrogen – hydrogen gas is produced
      ▪ If the metal is less reactive than hydrogen – the pure metal is produced (coats the cathode)
      o At the positive electrode (anode) – OHions & negative non-metal ions are present
      ▪ If halide ions are present – the halogen gas is produced
      ▪ If halide ions aren’t present – oxygen gas is produced (OH ions discharged)
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