Empirical Formula

IB chemistry standard level but also suitable for GCSE and A level chemistry

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Empirical formula

  • Shows the simplest whole number ratio of atoms of each element in a particle of the substance.
  • Example: a compound contains 40.00% Carbon, 6.73% hydrogen and 53.27% oxygen by mass. 
  • Determine the empirical formula: 
  • C= 40/12.01=3.33  
  • H=6.73/1.01=6.66 
  • O=53.27/16.00= 3.33 
  • Ratio is 3.33:6.66:3.33 = 1:2:1 
  • therefore empirical formula is CH20  
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In CH2O, the 2 is supposed to be subscript but I don't know how to do subscript on here

Suzie Mathis Jones


Thanks really helpful i actually understand this now!!!!!!

Sarah Catherine


So do I, never thought I would!

Caitlin Moutrie


I understand why you divide it by the atomic number but why is there .1 at the end?

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