Chapter 7 Section 4.1

​When a new substance is discovered, we analyze it to reveal the percentage composition

​Using this information we can determine an elements empirical formula

• ​Empirical formula consists of the symbols for the elements combined in a compound, with the subscripts showing the smallest whole number ratio of the different atoms in the compound

  • ​the simplest ratio of atoms

  • ​For an ionic compound this is the chemical formula

  • ​for molecular compound it may not always be the molecular formula

    • ​Diborane gase

      • ​Molecular formula: B₂H_6. Empirical formula: BH₃

​Quantitative analysis shows that a compound contains 32.38% sodium, 22.65% sulfur, and 44.99% Oxygen. Find the empirical formula

• ​First step: go from percentage composition to mass composition

  • ​32.38% Na = 32.38 g Na

  • ​22.65% S = 22.65 g S

  • ​44.99% O = 44.99 g O

• ​Second step: convert mass to moles