LESSON 2 - GRAVIMETRIC ANALYSIS

• What is the gravimetric method based on?


  Determining the mass of a pure compound
• What type of data does an analytical balance produce?

  Highly accurate and precise data
• What are the types of gravimetric methods?

  • Volatilization gravimetry
  • Precipitation gravimetry
  • Gravimetric titrimetry
  • Electrogravimetry
  • Atomic mass spectrometry
• What occurs in volatilization gravimetry?


  The analyte is volatilized at a suitable temperature
• What is precipitation gravimetry used for?


  Converting analyte to a sparingly soluble precipitate
• How is the analyte processed in gravimetric titrimetry?


  By determining the mass of a reagent needed
• What does electrogravimetry involve?


  Separation of analyte by deposition on an electrode
• What does atomic mass spectrometry use to separate ions?


  A mass spectrometer
• What are some applications of volatilization methods?

  • Moisture determination
  • Carbonate determination
  • Sulfides and sulfites determination
  • Combustion products (H2O and CO2)
• How is moisture determined directly?

  By collecting water on solid desiccants
• What is the indirect method of moisture determination?

  Determining water by mass loss during heating
• How is carbonate determined in a sample?

  By decomposing it with acids to release CO2
• What is the process for determining sulfides and sulfites?

  Collecting H2S or SO3 on an absorbent
• How are combustion products collected?

  By using weighed absorbents for H2O and CO2
• What is a mole used for?


  Counting atoms in samples of matter
• How many particles are in one mole?

  6.022 × 10²³
• What is the mass of 1 mole of 12C?

  12 g
• What is the relationship between mass, number of particles, and moles?

  • Divide by molecular weight to find moles
  • Multiply by molecular weight to find mass
  • Use Avogadro's number for conversions
• What is the unit for molecular weight?

  g/mol
• What is the gravimetric factor (GF)?


  Ratio of molecular mass of analyte to precipitate
• How is the percentage of analyte calculated?

  Using the gravimetric factor (GF)
• What does the gravimetric factor relate to in gravimetric calculations?

  The stoichiometric relation between analyte and precipitate
• What is the process for reporting results of gravimetric determination?

  • Results reported as percentage of analyte
  • Precipitate is often not the analyte
  • Related through the gravimetric factor (GF)