2 - Amount of substance

• Relative atomic mass is the weighted average mass of an atom of an element, taking into account naturally occurring isotopes, relative to 1/12th the mass of an atom of carbon-12.
• The relative molecular mass of a molecule is the mass of that molecule compared to 1/12th of the mass of an atom of carbon-12.
• Moles = mass/Mr

  Mass in g.
• Concentration = mol/vol

  Concentration is mol dm-3

  Volume is dm-3
• To go from cm3 to dm3, divide by 1000.
• PV = nRT

  P is pressure (Pa)

  V is volume (m3)

  n is number of moles

  R is the gas constant

  T is temperature (K)
• To find the mass of one atom of a substance (in g), divide the mass number by Avogadro's constant.
• Atom economy = mass of desired product/total mass of reactants x100
• Yield of a reaction = moles of a specified product/theoretical max number of moles of product

  Or

  grams of specified product obtained in a reaction/theoretical maximum