FINDING EMPIRICAL AND CHEMICAL FORMULAS BY EXPERIMENT

1
FINDINGEMPIRICAL AND CHEMICAL FORMULAS BY
EXPERIMENT

• Chemistry 11
• Ms. McGrath

2
Finding Empirical and Chemical Formulasby
Experiment

• We know how to find percentage composition of a
  compound using its chemical formula.
• Often, the chemical formula is not known.
• Experimentation is then used to determine the
  percentage composition, molar mass then the
  chemical formula.

3
Finding Empirical and Chemical Formulasby
Experiment

• Carbon- Hydrogen Combustion Analyzer
• An instrument that is used to analyze the amount
  of hydrogen, carbon and oxygen in important
  chemicals.
• It determines the percentage composition of
  compounds that are made up of these three
  elements.

4
Carbon- Hydrogen Combustion Analyzer
5
Carbon- Hydrogen Combustion Analyzer

• How does this work?

6
Carbon- Hydrogen Combustion Analyzer

• How does this work?
• Compounds containing carbon and hydrogen will
  burn in a stream of pure oxygen, O2, to produce
  only carbon dioxide and water.
• If a sample contains only carbon and hydrogen you
  can find the mass of the products (CO2 and H2O)
  separately to determine the mass percent of the
  compound.

7
Carbon- Hydrogen Combustion Analyzer
8
Carbon- Hydrogen Combustion Analyzer

• Example
• A 1.000 g sample of a pure compound, containing
  only carbon and hydrogen, was combusted in an
  analyzer. The combustion produced 0.6919 g of
  water and 3.338 g of carbon dioxide.
• Calculate the mass of carbon and hydrogen in the
  sample.
• Find the empirical formula of the compound.