gravimetric

• What is gravimetric analysis?

  A quantitative analysis method using weight
• How is the amount of a species determined in gravimetric analysis?

  By converting it to a weighable product
• What type of reactions are frequently used in gravimetric analyses?

  Precipitation reactions
• What is done with the precipitate in gravimetric analysis?

  It is filtered, dried, and weighed
• What are the advantages of gravimetric analysis?

  Its simplicity and accuracy
• What is the chief disadvantage of gravimetric analysis?

  It requires meticulous, time-consuming work
• What are the three fundamental types of gravimetric analysis?

  Precipitation, volatilization, electrogravimetry
• How does precipitation gravimetry work?

  The analyte is separated as a precipitate
• What occurs in volatilization gravimetry?


  The analyte is converted to a gas
• What is electrogravimetry?

  The analyte is deposited on an electrode
• What are the steps in gravimetric analysis after dissolving the sample?

  1. Preparation of the solution
  2. Precipitation
  3. Digestion
  4. Filtration
  5. Washing
  6. Drying or igniting
  7. Weighing
  8. Calculation
• What is involved in the preparation of the solution step?

  Adjusting pH and removing interferences
• What happens during precipitation?

  A precipitating agent is added to the sample
• What occurs during nucleation in precipitation?

  Molecules aggregate to form a nucleus
• What does the Von Weimarn ratio predict?

  Particle size is inversely proportional to supersaturation
• What is the formula for relative supersaturation?

  Relative Supersaturation = (Q – S) / S
• What conditions help achieve optimum precipitation?

  Use dilute solutions and slow addition
• What is digestion of the precipitate?

  Heating the precipitate to promote particle growth
• What is Ostwald ripening?

  Dissolution of small particles and reprecipitation on larger ones
• How can surface adsorption be reduced?

  By careful washing of the precipitate
• What is peptization?


  Loss of precipitate due to charge imbalance
• What should be used to wash colloidal precipitates?

  Dilute volatile electrolytes
• How can the common ion effect be used?

  To reduce the solubility of the precipitate
• What happens if excess precipitating agent is added?

  It may form a soluble complex with the precipitate
• How many moles of S$^{2-}$ are needed to precipitate 10 moles of Ag$^{+}$ as Ag$_{2}S$?


  1. 5 moles of S$^{2-}$
• What is the purpose of drying the precipitate?

  To remove remaining moisture
• What is the purpose of ignition in gravimetric analysis?

  To convert precipitate to a stable form
• Why is it important to know the empirical formula of the precipitate?

  To accurately determine the analyte amount
• How is the precipitate weighed accurately?

  By burning the filter paper away
• What is coprecipitation?

  Unwanted material precipitating with the analyte
• What is surface adsorption in gravimetric analysis?

  Unwanted material adsorbed onto precipitate surface
• What is occlusion in gravimetric analysis?

  Impurities trapped within growing crystals
• What is post precipitation?

  Contamination of precipitate by impurities
• What are the ideal characteristics of a gravimetric precipitating agent?

  Specificity and selectivity towards the analyte
• How do inorganic precipitating agents compare to organic ones?

  Inorganic agents are less selective but known formulas
• What is a disadvantage of organic precipitating agents?

  They form precipitates of unknown formula
• What is the gravimetric factor (GF)?

  Weight of analyte per unit weight of precipitate
• How is the weight of analyte calculated from gravimetric data?

  Weight of precipitate multiplied by GF
• What is the significance of gravimetric analysis?

  Provides precise analysis with minimal error
• What types of substances can be determined gravimetrically?

  Inorganic anions, cations, and organic substances