Spectroscopy

Question 1

List the four types of electrons that may be present in organic molecules.

Question 2

Which types of electrons are responsible for the absorption of UV/Vis radiation in UV/Visible
spectrophotometry.

Question 3

Which of the following molecules are likely to absorb radiation in the UV/Vis region, and why?
- Aspirin
- Cholesterol
- Hexane
- Paracetamol
- Sucrose
- Caffeine

Question 4

Explain the reasons why the Beer-Lambert Law may not be obeyed.

Question 5

Discuss what analytical techniques use the electromagnetic spectrum and indicate which region (wavelength range) of the electromagnetic spectrum is used in each technique.

Question 6

When is it suitable to use plastic cuvettes?

Question 7

When is it suitable to use glass cuvettes?

Question 8

When is it suitable to use quartz cuvettes?

Question 9

State the Beer-Lambert Law and explain each of the terms involved.

Answer 9

A = εcl
where
A = absorbance (no units)
ε = molar absorptivity
c = concentration (M)
l = sample path length (cm)

Question 10

Explain the difference between the following modes of atomisation in atomic absorption spectrometry (AAS):
Flame atomisation
Graphite furnace atomisation

Question 11

List the following in order of increasing wavelength:
- Gamma rays
- Visible spectrum
- Radiowaves
- X-rays
- UV-rays
- Infrared
- Microwaves

Question 12

In UV/Vis spectroscopy, what molecular orbitals do the electrons transition between?

Question 13

Explain how the hollow cathode lamp emits mono-chromatic radiation.