chapter 3 - amount of substance

• relative atomic mass-

  mass of one of its atoms relative to 1/12th the mass of one atom of carbon-12
• relative molecular mass-

  mass of one molecule relative to 1/12th the mass of an atom of carbon-12

  same as relative formula mass
• nitrate NO3-

  carbonate CO3 2-

  sulfate SO4 2-

  hydroxide OH -

  ammonium NH4+

  phosphate PO4 3-

  nitrite NO3-

  sulphite SO3 2-

  hydrogen carbonate HCO3 -

  dichromate Cr2O7 2-

  manganate (permanganate) MnO4
• empirical-

  shows the relative numbers of atoms of each element present using the smallest whole numbers of atoms
• at the same temp and pressure equal volumes of gas contain the same number of moles

  when you measure gas volume you're indirectly counting the no of molecules
• assumptions of the ideal gas equation

  • random motion
  • elastic collisions
  • negligible size
  • no intermolecular forces
  • most people presume room temp is 25 degrees c or 298K
• assumptions of ideal gas equation

  • all collisions are perfectly elastic
  • there is no intermolecular forces
  • molecules are of negligible size
  • molecules have random motion
• the ratio will say the max percentage yield but this is usually inaccurate

  • may not all have reacted
  • side reactions may have taken place
  • purifying product may result in loss of product
  • product could be left inside the reaction vessel
• reactant not in excess is the limiting reactant, you can compare the moles to figure this out

  atom economy measures how well atoms are utilized.

  high atom economy will make a large proportion of desired products and little unwanted waste products. also helps sustainability and best use of natural resources
• unlikely to have 100% yield

  • raw materials = impure
  • product left in the apparatus
  • the reaction may not finish
  • may have unexpected side products from side reactions
  • in reversible reactions some products may turn back into reactants (e.g haber process)
• advantages of atom economy

  • environment- waste can be bad especially if toxic
  • profit- waste products can be expensive to dispose of, reactions w low atom economy use up raw materials quickly so more of them are needed
  • sustainability- if raw materials = non renewables they will run out. happens faster in low atom economy processes