Amount of Substance

• working out concentration of acid or alkali with titrations:

  • use pipette to measure a set volume of solution
  • put in flask and add drops of indicator
  • fill burette with standard solution of acid
  • use funnels to pour acid into burette
• two main indicators?

  • methyl orange - red in acid, yellow in alkali
  • phenolphthalein - colourless in acid, pink in alkali
• a mole?


  large numbers of particles
• amount of substance measured by mole (mol)
• Avogadro's constant: 6.022 x 10^23
• number of particles = number of moles x Avogadro's constant
• moles = mass / Mr
• concentration of solution is how many moles are dissolved per 1dm3 of solution. units: mol dm-3
• moles = concentration x volume
• cm3 --> dm3?


  divide 1000
• pV = nRT

  pressure x volume = number of moles x 8.31 x temperature
• 1cm3 = 1 x 10^-6 m3
• 1dm3 = 0.001 m3
• K = C + 273
• standard solution: any solution that you know the exact concentration
• percentage yield = actual yield / theoretical yield x 100
• percentage yield tells you how wasteful a process is
• atom economy?


  measure of proportion of reactant atoms that's part of the desired product in balanced chemical equations
• atom economy = molecular mass of desired product / sum of molecular masses of all x 100
• companies use processes with high atom economies:

  • better for environment, produce less waste
  • more efficient use of raw materials, more sustainable
  • less expensive
• mass spectrometer?


  an analytical technique used to identify unknown compounds
• mass spectrometer is most useful instrument for accurate determination of the relative atomic mass of an element - based on abundance and mass of each of its isotopes
• mass spectrometer can be used to find the relative molecular mass of molecules
• when sample passes through the mass spectrometer, a spectrum is produced of mass/charge ratio against abundance
• spectrum can be used to find the relative isotopic abundance, atomic and molecular mass and structure of a compound
• base peak?

  peak with the highest mass is the molecular ion peak, Mt, and the peak which has the largest abundance (tallest peak)
• mass spectrometer is based on an ionised sample being accelerated through the mass spectrum, and being separated based on the ratio of their charge o their mass.
• volumetric analysis?


  a process that uses the volume and concentration of one chemical reactant (standard solution) to determine the concentration of another unknown solution
• standard solution?


  a chemical solution with a precisely known concentration
• steps in a titration:

  • measuring a known volume of one of solutions with a volumetric pipette and placing it into a conical flask
  • other solution placed in burette
  • drops of indicator are added
  • tap on burette is carefully opened and solution is added - portion by portion - to the conical flask until indicator changes colour
  • repeat until concordant results are obtained
• Relative Atomic Mass: The average mass of one atom of an element relative to 1/12th the mass of one atom of C-12