viva

• Principle of volumetric analysis:

  • Concentration of a solution is determined by allowing a known volume of this to react quantitatively with another solution of known concentration
• Titration:

  • Process of adding one solution from the burette to another in the titration flask to complete the chemical reaction involved
• Indicator:

  • Chemical substance that changes colour at the end point
• End point of titration:

  • Stage during titration at which the reaction is just complete
• Primary standard substances:

  • Available in high degree of purity, stable and unaffected by air, does not gain or lose moisture, readily soluble and solution in water remains as such for a long time
  • Examples: crystalline oxalic acid, anhydrous Na2CO3, Mohr’s salt
• Burette and pipette rinsing:

  • Rinsed with the solution they are filled with to remove any substance sticking to their sides, which could decrease the volume of liquids to be taken in them
• Reading meniscus:

  • Lower meniscus for colourless and transparent solutions
  • Upper meniscus for highly coloured solutions
• Normal solution:

  • Solution containing 1 gm-equivalent of solute per litre, symbolised as 1 N
• Last drop of solution in pipette:

  • Must not be blown out as it is extra volume measured by the pipette
• Holding pipette:

  • Should never be held from its bulb to avoid introducing errors due to expansion from body heat
• Acidimetry and alkalimetry:

  • Branch of volumetric analysis involving chemical reaction between an acid and a base
• 1.0 M solution:

  • Solution containing 1 mole of solute per litre
• Concordant readings:

  • Readings that differ by less than 0.05 mL in volumetric analysis
• Difference between end point and equivalence point:

  • End point: visible change indicating completion of reaction
  • Equivalence point: stoichiometric amounts of reactants added, may or may not coincide with visible end point
• Indicator in titration of oxalic acid with sodium hydroxide:

  • Phenolphthalein
  • Sodium hydroxide solution in burette
  • End point: appearance of pink colour
• Indicator in titration of sodium carbonate against hydrochloric acid:

  • Methyl orange
  • Acid solution in burette
  • End point: change of colour from yellow to pinkish red
• Basicity of an acid:

  • Number of replaceable hydrogen atoms in a molecule of the acid
• Relation between equivalent mass of acid and its molecular mass:

  • Equivalent mass of acid = Molecular mass / Basicity
• Acidity of a base:

  • Number of OH- ions furnished by a molecule of the base
• Relation between equivalent mass of a base and its molecular mass: