1.24 calculate empirical and molecular formulae from experimental data

Empirical formulae – simplest whole number ratio of atoms in a compound

Molecular formulae – the exact nu,her of atoms in a molecule (the formula) 

When creating formulae, remember to always use subscript numbers! 

Calculating Empirical formulae –

  1. Divide by mass number
  2. Divide by smallest number
  3. Work out ratio
  4. Write empirical formula 

Worked example: Iron Oxide – 

  1. Iron = 2.24g / 56 (RFM) = 0.04
  2. Oxygen = 0.96g / 16 (RFM) = 0.06
  3. Divide both number products by 0.04, as it is the smallest number.
  4. The outcome of Oxygen, 0.06 / 0.04 = 1.5, you must multiply this to become a whole number – 3 
  5. You must do the same to Iron, 1 x = 2
  6. Write empirical formula = Fe2O3 
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