Gravimetric

• What is gravimetric analysis?

  Quantitative determination of analyte concentration
• How is the analyte determined in gravimetric analysis?

  By converting it to a product and weighing
• What does "gravi" and "metric" refer to in gravimetric analysis?

  Gravi means weighing; metric means measure
• What is one application of gravimetric analysis?

  Chemical analysis of ores and industrial materials
• Why is gravimetric analysis considered more accurate than volumetric analysis?

  It avoids problems with calibration errors
• What is a disadvantage of gravimetric analysis?

  It is time-consuming
• What is the role of precipitation in gravimetric analysis?

  To convert analyte to a solid for weighing
• What is one type of instrument used in gravimetric analysis?

  Crucible
• What is the importance of pH in sample preparation?

  It influences the solubility of the precipitate
• How does temperature affect the precipitation process?

  Higher temperature increases solubility of precipitate
• What is supersaturation in the context of precipitation?

  It increases nucleation during the precipitation process
• What is nucleation?

  Coalescence of ions to form "nuclei"
• What is digestion in gravimetric analysis?

  Keeping precipitate in solution to encourage growth
• Why should colloidal precipitate be avoided?

  It is difficult to wash and filter
• What is occlusion in the context of impurities?

  Trapping of impurities within the crystal
• What is surface adsorption?

  Impurities adhering to the surface of precipitate
• What is post precipitation?

  Formation of a second precipitate from mother liquor
• What is isomorphism in gravimetric analysis?

  Replacement of one ion by another in crystals
• What is the purpose of washing the precipitate?

  To remove co-precipitate impurities
• What is the significance of drying the precipitate?

  To remove physically-bound water before weighing
• What is the formula for calculating purity in gravimetric analysis?

  % Purity = $\frac{W \times E}{S} \times 100$
• If 0.3160 g of NaCl yields 0.7732 g of AgCl, how would you compute for NaCl?

  Use the gravimetric method formula
• How would you calculate the HgCl2 content from 0.2551 g of mercury bichloride yielding 0.1815 g of HgS?

  Apply the gravimetric method formula
• How would you compute the percentage purity of KI from 0.47 g sample yielding 0.7564 g of AgI?

  Use the gravimetric method formula
• What instruments are used in the precipitation method of gravimetric analysis?

  Desiccator, crucible, drying oven
• What instruments are used in the volatilization method of gravimetric analysis?

  Distillation setup, hydrostatic scale
• What factors must be considered during the preparation of the sample solution?


  Volume, pH, and temperature
• What happens if excess volume of solution is used during precipitation?

  It leads to coagulation of the precipitate
• What is the relationship between supersaturation and nucleation?

  Increased supersaturation leads to increased nucleation
• What is the purpose of digestion in the precipitation process?

  To encourage densification of nuclei
• What is the effect of proper precipitation technique on surface adsorption?

  It reduces surface adsorption and impurities
• What is the significance of washing the precipitate after filtering?

  To remove co-precipitate impurities
• Why is it important to dry the precipitate before weighing?

  To remove physically-bound water
• What is the role of organic precipitating agents in gravimetric analysis?

  They form slightly insoluble chelates with metal ions