Mass, Calculations + Analysis

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  • Mass, Calculations + Analysis
    • Mass of Atoms
      • Relative mass of protons + neutrons is 1
      • Atomic number = number of protons
        • same as number of electrons
      • Mass number = protons + neutrons in nucleus
      • Isotopes version of same element with different number of neutrons
    • Masses of Atoms and Moles
      • Atoms too small to weigh
        • use relative atomic mass
          • Average value for isotopes of an element
          • Ar
      • Relative formula mass = all the relative atomic masses added up in a compound
        • eg. The Mr of CaCl2
          • Ar of Ca = 40
            • Mr = 111
          • Ar of Cl x 2 = 71
            • Mr = 111
        • Mr
    • Percentages and Formulae
      • Relative atomic mass of element in compound used to wok out percentage composition
        • eg. Percentage of carbon in CO2
          • Ar of C = 12
            • Mr = 44
              • Percentage = (12 / 44)x100
                • 27.3%
          • Ar o O x 2 = 32
            • Mr = 44
              • Percentage = (12 / 44)x100
                • 27.3%
      • Emperical formula is the symbol of the compound, ie. CH3 or CaCl2
        • Work out with given masses or percentage composition
        • eg. Emperical formula of hydrocarbon that contains 80% carbon
          • Mass in 100 grams
            • Carbon = 80
            • Hydrogen = 20
            • Divide mass by Ar
              • 80/12 = 6.67
              • 20/1 = 20
              • Divide by smallest number
                • 6.67/6.67 = 1
                • 20/6.67 = 3
                • Emperical formula =
                  • CH3
    • Yield
      • Tells you how much is made
      • The percentage yield tells you the max amount that could be made
        • calculated before reaction takes place
      • percentage yield =
        • amount of product / max amount
          • maximum amount is calculated from the balanced equation
      • In industry, high percentage yield needed
        • Reduce waste  and pollution
    • Gas Chromatography - C2
    • Analysing a substance for addiitves or food colouring
      • mass spectrometry

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