organic analysis

• What is the purpose of quantitative analysis in determining purity?

  To determine purity and quality of a product using numerical data.
• What does qualitative analysis aim to determine?


  It aims to determine the identity of chemicals present in a substance.
• What is used to determine the purity of a solid sample?

  Melting point (mpt).
• What is used to determine the purity of a liquid sample?


  Boiling point (bpt).
• What are the two main outcomes when analyzing purity based on melting point or boiling point?

  • Sample has fixed, sharp value for bpt/mpt = PURE sample
  • Mpt across a range, rather than a single discrete value = IMPURE
• What is the melting point range for a pure solid?

  A pure solid has a melting point range within 0.5 - 2 °C.
• How do impurities affect the melting point of a substance?

  Impurities lower the melting point and cause it to melt across a larger range of temperatures.
• What is the melting point of pure ice?

  0 °C.
• What happens to the melting point of ice formed in the sea?

  The melting point of sea ice is between -2 °C and -4 °C.
• What is the technique for determining melting point?

  • Dry solid sample and force it into a capillary tube.
  • Place in an electronic melting point device that raises temperature until melting occurs.
  • Observe the sample through a magnified image to see when melting starts and finishes.
• What is the principle behind simple distillation?

  It is used to separate and purify liquids based on boiling point.
• What is the minimum boiling point difference required for simple distillation?

  Greater than 50 °C.
• What does it indicate if no distillate is collected at the expected boiling point?

  It indicates that the substance is not present.
• What does it indicate if the distillate is collected at a boiling point higher than expected?


  It indicates the presence of impurities.
• What is the principle behind fractional distillation?

  • Used to separate liquid mixtures with components closer in boiling points.
  • Boiling point is characteristic for a compound and can be compared with known values.
• What is volumetric analysis?

  It is an analytical technique used to determine the concentration of a dissolved substance.
• What is a standard solution?

  A standard solution is a solution of accurately known concentration.
• What is a primary standard?

  A primary standard is a substance so pure that the amount can be calculated accurately from its mass.
• What are the properties of a primary standard?

  • Known chemical formula.
  • Higher molar mass to minimize weighing errors.
  • Easy to store without deteriorating.
  • Soluble in solvent (usually water).
  • Inexpensive and readily obtainable in pure form.
• What is the purpose of conducting redox volumetric analysis?

  To determine the unknown concentration of an oxidizing agent and reducing agent.
• What is the equivalence point in a titration?

  The equivalence point is when the reactants react completely in the mole ratio indicated by the balanced chemical equation.
• What is the end point in a titration?

  The end point is the point during titration where the indicator changes color.
• Why is it often unnecessary to add an additional indicator in redox titrations?


  Some compounds used as primary or secondary standards undergo a color change of their own when the reaction occurs.
• What are some examples of indicators used in redox titrations?

  • Potassium permanganate (KMnO4): changes from purple to pink to colorless.
  • Potassium dichromate (KCr2O7): changes from orange to green.
  • Starch: used when iodine is the titrant, forming a blue-purple color when I2 is reduced.
• What is the difference between the end point and equivalence point?

  The end point is when the indicator changes color, while the equivalence point is when reactants react in the correct mole ratio.
• What calculations are involved in redox titrations?

  1. Half equations.
  2. Overall balanced redox equation.
  3. Average titre.
  4. n (standard) = cv → mole ratio.
  5. n (unknown) = cv.
• Why is dilution performed in volumetric analysis?

  • To obtain a concentration that results in titres within the range of the burette.
  • Dilution factor = \(\frac{\text{volume of diluted solution}}{\text{volume of undiluted solution}}\).
• What are the steps involved in calculating concentrations during dilution?

  1. Draw a diagram to represent dilution.
  2. Use n(standard) = cv
  3. n(unknown) = n(standard) x UOK
  4. [unknown] diluted (sample)= n/v (mol/L)
  5. Calc [unknown] undiluted

  [unknown] diluted = [unknown] diluted (sample)

  [unknown] undiluted = [unknown] diluted x (v(diluted)/v(undiluted))
• How do you convert between mol/L and g/L concentrations?

  • To convert from mol/L → g/L: Concentration x molar mass = g/L
  • To convert from g/L → mol/L: Concentration / molar mass = mol/L
• Where does the aliquot and titre come out from?

  aliquot = pipette

  titre = burette
• What states can the analyte be in for mass spectrometry?

  The analyte can be solid, liquid, or gas.
• What is mass spectrometry?

  analytical tool useful for measuring mass-to-charge ratio (m/z) of one or more molecules present in a sample

  • used to determine structure of proteins + drugs
• What are the features of a mass spectrum?


  • Vertical axis: relative intensity
  • horizontal axis: mass-to-charge (m/z) ratio
  • Molecular ion peak → indicates molar mass of the molecule
  • Fragment ions appear as other peaks with smaller m/z values.
  • Base peak → most intense peak (intensity of 100%).
• What does the molecular ion peak represent in a mass spectrum?

  The molecular ion peak represents the molar mass of the molecule.
• What happens to neutral molecules in a mass spectrometer?

  They are vacuumed out of the machine
• How are ions separated in a mass spectrometer?

  Based on their mass-to-charge (m/z) ratio
• What does the detector in a mass spectrometer measure?

  The number of ions with different m/z values
• What is the role of the electric field in a mass spectrometer?

  To accelerate positive ions
• How do ions move in a magnetic field in a mass spectrometer?

  In a curved path with a radius depending on their mass-to-charge ratio
• What does the molecular ion peak represent in a mass spectrum?

  It indicates the molar mass of the molecule