Unit 1.3

• me


  % elfor
• 21105 reading
• PV = nRT


  Equation for ideal gas law
• R


  Economy toral mr of reactants
• P = pressure


  V = volume, n = no of moles, T = temp (K)
• Avogado


  % yield
• Obtained


  Maximum theoretical yield
• nod atoms


  per mole
• Mass


  Element PH
• Aconc


  C x V *(dm³)#
• A


  Mir x mol
• Mass


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• the machine without hitting air molecules so a vacuum is needed inside the apparatus
• Calculating relative atomic mass

  1. Data from mass spectrometry

  2. Weighted average of masses of all atoms in isotopic mixture
• relative atomic mass = (1.40 x 204)+(24.1 x 206)+(22.1 x 207) + (52.4 x 208) = 207.2
• Other uses of mass spectrometry

  • Identifying unknown compounds
  • Identifying trace compounds in forensic science
  • Analysing molecules in space
• Interpretation of mass spectra

  1. Electron knocked off molecule to form positive molecular ion

  2. Molecular ions are energetically unstable and break up into fragments

  3. Wide range of fragment ions possible
• Chlorine gas consists of molecules, not individual atoms
• Peaks in the ratio 33:961 in chlorine mass spectrum
• Peak A is due to 35Cl, peak B is due to 37Cl
• Probability of 35Cl is 3 times that of 37Cl, so peak heights are in 3:1 ratio
• Peak C (m/z 70) is due to 35Cl-35Cl, peak D (m/z 72) is due to 35Cl-37Cl or 37Cl-35Cl, peak E (m/z 74) is due to 37Cl-37Cl
• Ratio of peaks C:D:E is 9:6:1
• Boron has two isotopes, the molecular ion region of its mass spectrum shows peaks in the ratio 1:2:1