Topic 3: FTIR

Question 1

What are some of the points that Beer’s Law does not account for?

Answer 1

Light scattering and other losses that reduce beam of light

Question 2

What are the real limitation of Beer’s law?

Answer 2

• High concentrations (>0.01 M) analytes intact and alter properties, which results in non-linear calibration
• Salts and other electrolytes also a factor
• Ɛ is dependent on the refractive index of the medium and the refractive index is dependent on the solution composition. Not a significant problem for concentrations less than 0.01 M

Question 3

What are the apparent limitations?

Answer 3

• When analyte chemically reacts (or associates) with solvent
• Beer’s law applies to monochromatic radiation
  
  • Molecular species produce “broad” bands
  • Stray light can also cause a deviation from linear Beer’s law.

Question 4

Illustrate singlet and triplet excited state, using electronic states. Which one has the lowest energy?

Answer 4

Question 5

Explain the theory of photoluminescence. Use the diagram to explain it.

Question 6

Explain the diagram below.

Question 7

Explain why the energy of absorption is larger than energy of emission