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