Anachem Expe:5

• Volumetric method


  A technique in which the result of analysis depends upon the accurate measurement of the volume of an added chemical reagent of known concentration through the process of titration
• Volumetric process


  • Rapid technique compared to other analytical methods
  • Yields very reliable results
• Titration


  A process whereby a standard delivered through an apparatus called burette is brought into reaction with an analyte in solution
• Titration


  Used to determine volumetrically, the concentration of the desired substance in solution by adding a standard solution of known volume and concentration until the reaction is complete, usually by a color change due to a chemical indicator
• Volumetric process


  1. Accurate weighing of the sample using an analytical balance (for solids)

  2. Accurate measurement using a pipette (for liquids)

  3. Bringing the sample into solution

  4. Removal/ separation of interfering substance, if any

  5. Addition of indicator

  6. Titration of the analyte using standard solution
• Classifications of volumetric process

  • Neutralization
  • Oxidation-Reduction or Redox
  • Precipitation (Precipitimetry)
  • Complex Formation (Compleximetry)
• Methods for direct determination of a substance of interest

  • Direct method
  • Indirect method
• Direct method


  The substance of interest is directly determined by titration with a standard solution
• Indirect method


  A known quantity of a reagent is added that reacts with the substance of interest, the excess of which is determined by direction of a standard solution
• Neutralization


  A reaction between an acid and a base, based on the union of the hydrogen ion from the acid and the hydroxyl ion from the base to form water
• Acidimetry


  Titration of an acid sample with a base
• Alkalimetry


  Titration of a base sample with an acid
• Equivalence point


  The point at which the amount of the titration added is stoichiometrically equivalent to the analyte
• End point


  The point at which a chemical indicator changes color, which must coincide with the equivalence point
• Common indicators for neutralization

  • Phenolphthalein (Hph)
  • Methyl orange (MO)
• Phenolphthalein


  Dark pink in basic solution, colorless in acid solution
• Methyl orange


  Red-orange in basic solution, yellow in acid solution
• Titrimetry


  Determination of analyte by reaction with measured amount of standard reagent
• Standard Solution (titrant)


  Reagent of known concentration
• Titration


  Slow addition of titrant to analyte solution from a volumetric vessel (buret)
• Equivalence Point


  Reached when amount of added titrant is chemically equivalent to amount of analyte present in the sample
• End Point


  The occurrence of an observable physical change indicating that the equivalence point is reached. Might differ from Equivalent point.
• Hydrogen Ion - from acid
• Hydroxyl ion - from base to form water