calculations

• empirical formulas

  shows simplest or lowest ratio of atoms present in the compound 


  working out

  1. column headings
  2. mass
  3. Ar
  4. mass ratio
  5. divide both answers by lowest one
  6. * if answer if a decimal multiple by lowest number to remove decimal e.g

  
• Ar, Mr

  Ar- relative atomic mass

  shown on periodic table

  Mr- relative molecular mass

  mass of molecule

  sum of all masses of the atoms in the compound

  calculated like;

  
• % composition by mass =

  total mass of elements in compound

  ———————————————TIMES 100

  total mass of compound
• reacting mass calculations

  used to

  • calculate mass of a product from a known mass of a reactant

  • calc a mass of a reactant needed to make a known mass of a product

  method

  1. ar/mr values
  2. add in mass units
  3. start w ✔︎ divide 1g then multiply to total in question

  ✔︎ = mass given

  ? = the one we have to find out