PHA 039:Precipitation Titration, Redox Titration, Gravimetry

• Gravimetric Analysis


  Determining the weight of a substance in a sample from the weight of a chemically equivalent amount of some other substance
• Titrimetric Analysis / Volumetric Analysis


  The volume or mass of a standard reagent required to react completely with the analyte was measured
• Standard Solution / Titrant


  A reagent of known concentration that is determined by standardization
• Titration


  Slowly adding a standard solution from a buret or other liquid dispensing device to a solution of the analyte until the reaction between the two is judged complete
• Primary Standard Volumetric Solution


  Chemical solutions that have already attained 100% purity and does not require standardization
• Potassium Iodate (KIO3) is an example of Primary Standard Volumetric Solution
• Standardization


  The process of determining the exact concentration of the titrant using standards
• Primary Standard


  • Extremely pure
  • Highly stable
  • Readily available and cheap
  • Preferred to be of high molecular weight to provide higher accuracy when weighing
• Secondary Standard


  • Less pure than primary standard
  • Less stable than primary standard
  • Can not be weighed easily
• Analyte / Titrand


  The solution of unknown concentration that is being analyzed
• Indicators


  Weak acids or bases whose solutions can change color due to changes in pH and are used to determine the end points in neutralization processes
• Endpoint


  The point at which the reaction is observed to be complete, indicating the equivalence point has been reached
• Pipette


  A laboratory instrument used to measure out or transfer small quantities of liquid, in volumes of milliliters (mL) and microliters (μL)
• Erlenmeyer Flask


  A container used to collect the solution under test, with a conical shape that allows for more vigorous swirling and minimizes spill hazards
• Beaker


  A cylindrical container with a flat bottom and a small spout to aid pouring, used to hold and transfer the standard solution into the top opening of a burette with help of a funnel
• Procedure


  1. Clean and assemble the buret

  2. Mount it in the ring stand and secure it with a buret clamp

  3. Make sure the stopcock is closed when filling the buret with the titrant

  4. Use a beaker with a funnel to prevent spilling the titrant

  5. Pipette the analyte into Erlenmeyer flask and add an indicator

  6. Place the flask on top of white paper to help visualize the end point

  7. Drain some titrant through the stopcock into a waste beaker to remove air bubbles

  8. Read the initial volume of the buret

  9. Slowly open the stopcock and add titrant to the analyte solution, stirring thoroughly

  10. Continue adding titrant in small quantities, adding dropwise near the endpoint

  11. The endpoint is signaled when a permanent color change is observed
• Data and Results


  1. Record the initial and final volume in the buret

  2. Subtract the initial volume from the final volume to determine the volume of titrant added

  3. Use standard chemical calculation methods such as Normality and Purity to determine the concentration of analyte
• Types of Titrants

  • One Titrant and Two Titrant
• Types of Titration based on Endpoint

  • Visual Titration and Potentiometric Titration
• Types of Chemical Reactions in Titration

  • Acid-Base / Neutralization
  • Reduction-Oxidation
  • Precipitation
  • Complexation
• Acid-Base Titration


  Used to determine the unknown concentration of an acid or base by precisely neutralizing it with an acid or base of known concentration
• Types of Acid-Base Titrimentry

  • Based on Titrant used (Acidimetry, Alkalimetry)
  • Based on Media used (Aqueous titration, Non-aqueous titration)
• Acidimetry


  Conducted by introducing a standard acid solution, gradually from a burette into a solution of the base being assayed, until chemically equivalent amounts of each have reacted
• Types of Acidimetry


  • Direct Acidimetry (Direct Aqueous, Direct Non-aqueous)
  • Residual Acidimetry (Residual Aqueous, Residual Non-aqueous)
• Alkalimetry


  Conducted by introducing a standard base solution, gradually from a burette into a solution of the acid being assayed, until chemically equivalent amounts of each have reacted
• Types of Alkalimetry

  • Direct Alkalimetry (Direct Aqueous, Direct Non-aqueous)
  • Residual Alkalimetry (Residual Aqueous, Residual Non-aqueous)
• Ostwald's Theory


  The color change of any indicator is due to its ionization, where the unionized form has a different color than the ionized form
• Quinonoid Theory


  Acid-base indicators exist in two forms, benzoid and quinonoid, which have different colors and interconvert based on the medium
• One Titrant (Direct Titration)


  Conducted by introducing one standard solution
• Visual Titration 


  Indicator solution (T.S)
• Potentiometric Titration


  pH meter glass electrodes
• Standard ACID solution 


  Titrant of Acidimetry
• Water


  Solvent for aqueous acidimetry is
• Solvent for Non-aqueous Acidimetry

  Neutral Solvent and Acidic Solvents
• Neutral Solvents

  Acetonitrile, Alcohols, Chloroforms, Benzene, Dioxane, Ethyl Acetate
• Acidic Solvent

  Formic acid, Glacial acetic acid, Propionic acids, Acetic anhydride, Sulfonyl chloride