F321

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  • Created by: FreyaBee
  • Created on: 05-12-12 09:42
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  • F321
    • Atomic Masses
      • Relative isotopic mass = mass of an istope compared with 1/12 mass of carbon-12
      • Relative atomic mass (Ar) = The weighted mean mass of an atom of an element compared with 1/12 the mass of carbon-12
      • Relative formulamass = weighted mean mass of a formula  unit compared with 1/12 Carbon-12
      • Relative Molecular Mass (Mr) = Weighted mean mass of a molecule compared with the mass of 1/12 cabon-12
    • Moles (n)
      • Avagadro's Constant
        • The number of atoms per mole of the carbon-12 istotope
        • 6.02 x 10^23 mol^-2
      • Working out moles
        • Gas
          • |STP| n=V(in cm3)/22,400
          • |RTP| n=V(in cm3)/24,000
          • Equal volumes of gases at the same temp and pressure  = equal number of molecules
        • Solid
          • moles = mass/molecular mass
          • n=m/M
      • Amount of any substance containing as many particles as there are carbon atoms in 12g of carbon-12.
        • Molar mass (M) = Mass per mole of a substance
          • Found by adding together relative atomic masses
    • Formulas
      • Empirical formula
        • Smallest whole number ratio of atoms of each element present in a compound
        • Always used for compounds with giant structures
        • Found by dividing by smallest value
      • Molecular Formula
        • Actual number of atoms of each element  in a molecule
      • Molecules
        • small group of atoms held together   by covalent bonds

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