Standard solutions-PHAY0002

• What is the British Pharmacopoeia (BP)?


  A comprehensive book that includes standards for raw materials used in pharmaceutical substances
• What does the British Pharmacopoeia provide guidelines for?


  Preparation, testing, and standardization of substances to ensure quality and safety
• What are the requirements for chemical processes in pharmaceutical analysis?


  • Specific to the substance being analyzed
  • React faster than the rate of reagent addition
  • Include a suitable indicator to signal completion
• What is the purpose of an indicator in chemical analysis?

  To signal the completion of the reaction, often through a color change
• What is titration in pharmaceutical chemistry?

  A technique to determine the concentration of a substance by adding a reagent of known concentration
• What are standard solutions?

  • Solutions of exactly known concentration
  • Referred to as "volumetric standards" in the BP
• How are standard solutions prepared?

  By weighing a known mass of a pure substance and dissolving it in a solvent to a known volume
• How can a 0.1M sodium hydroxide solution be prepared?

  By dissolving a known mass of pure NaOH in water and making it up to a specified volume
• What are the criteria for primary standards?


  • Chemically pure
  • Stable to heat
  • Non-hygroscopic
  • High molecular weight
  • Readily soluble in the solvent
  • Testable for impurities
• What is an example of a primary standard in the BP?


  Benzoic Acid
• Why are anhydrous compounds preferable as primary standards?

  Because hydrated substances can lose water of hydration, making their composition uncertain
• What is a secondary standard?


  A standard solution whose concentration is determined by titration against a primary standard
• How is hydrochloric acid (HCl) standardized?

  By titration with sodium bicarbonate (NaHCO₃)
• What are the types of titrations mentioned?

  • Acid-Base Titrations
  • Acidimetry: Titration of free bases using a standard acid
  • Alkalimetry: Titration of free acids using a standard base
• What is the role of indicators in titrations?

  To detect the end-point by showing a color change
• What occurs in redox reactions?

  • One component is oxidized
  • Another component is reduced
• What is oxidation in terms of electron transfer?

  Loss of electrons
• What is reduction in terms of electron transfer?

  Gain of electrons
• What is an example of oxidation in a chemical reaction?

  The oxidation of iron: $\text{Fe}^{2+} \rightarrow \text{Fe}^{3+} +$$e^-$
• What is a common oxidising reagent used in pharmaceutical analysis?

  Potassium Permanganate (KMnO₄)
• What is the standard concentration of potassium permanganate?

  0.02M
• What color does potassium permanganate appear when added to a solution?

  Pink
• What happens to the color of potassium permanganate at the end-point of a titration?

  It becomes colorless when all the permanganate has reacted
• What are complexometric reactions?

  Reactions that involve the formation of a complex between a metal ion and a chelating agent
• What is a chelating agent?


  A chemical compound that binds tightly to metal ions
• What is the most common titrating agent used in complexometric reactions?

  EDTA
• What type of complex does EDTA form with metal ions?


  A 1:1 complex
• Are precipitation reactions commonly used in titrations?


  No, they are not the most commonly used
• What is produced when silver nitrate reacts with halide ions?


  An insoluble product such as silver chloride
• What does a titration involve?


  The measurement by volume of a reagent of known concentration that reacts with the substance being determined
• What are the typical steps involved in a titration?


  1. Use a known mass or volume of sample in a conical flask and dissolve in water
  2. Add the indicator
  3. Add the titrant from a burette until the indicator changes color (end point)
  4. Calculate the amount of substance of interest from the volume of titrant added
• What is an indirect titration?


  A titration method used when substances cannot be titrated directly due to slow reactions
• What is a back titration?


  A method where a known quantity of a standard solution is added in excess to the sample and allowed to react. The amount of excess reagent remaining after the reaction is determined by another suitable standard solution. The difference between the amount of reagent A determined by titration and the original amount gives the amount used by the sample
• How do you determine the excess of reagent in a back titration?


  By titrating with another suitable titrimetric solution
• What is the significance of the difference in titration volume in a back titration?


  It relates to the amount of sample present
• Can titrations be performed without using water?


  Yes, non-aqueous titrations can be performed
• Why might a titration with water not give a sharp end-point with weak bases?

  Excess water may not be sufficiently acidic enough
• What happens when an amine is dissolved in water and titrated with a strong acid?

  The lone pair on the nitrogen reacts with H3o-, but protons can also react with water
• What is the consequence of protons having a choice to react with nitrogen or oxygen during titration?

  It leads to a lack of a sharp end-point
• What are the most common primary standard acids and bases used?

  Standard acids: benzoic acid & potassium hydrogen phthalate

  
  

  Standard bases: sodium carbonate