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Empirical formula vs Molecular formula🧮

Chemical formulas come in two forms. One gives the simplest ratio, the other gives the true number of atoms.

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Empirical formula
  • Shows the simplest whole-number ratio
  • Reduced to lowest terms
  • Found from percentage composition
  • Same for related compounds
  • Example: CH for benzene
🧮Molecular formula
  • Shows the actual number of atoms
  • A whole-number multiple of the empirical
  • Found using the molar mass
  • Unique to the specific compound
  • Example: C6H6 for benzene

Verdict

The empirical formula gives the simplest ratio; the molecular formula gives the real count. Multiply the empirical formula by a whole number, found from molar mass, to get the molecular one.

Frequently asked

How do I get the molecular formula?+

Find the empirical formula, then multiply it by molar mass divided by empirical mass.

Can they be the same?+

Yes. For water, both the empirical and molecular formula are H2O.

What does the empirical formula come from?+

It is calculated from the percentage composition by mass of each element.

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