Topic 22 - Analytical Techniques

Question 1

Which compunds can absorb IR radiation?

Answer 1

compounds with polar covalent bonds

Question 2

What to coupounds do when they absorb IR radiation and why?

2 types

Answer 2

They vibrate because the radiation is not energetic enough. They either undergo bending vibration or stretching vibration

Question 3

Why are molecyles that can absorb IR radiation responsible for enhanced global warming?

Answer 3

when the eart reflects back the Infra red radiation, these molecules absorb the radiation. This radiation increases their kinetic energy casuing the gases to heat up and the temperature of the Earth to heat up

Question 4

How does IR spectroscopy work?

Answer 4

Differnet functional groups absorb different frequencies of IR radiation, so a graph of frequencies against transmittance/absorbence is plotted

Question 5

What is the fingerprint reigon?

Answer 5

region below 1500 cm^-1

Question 6

Uses of IR spectroscopy

and why

Answer 6

• monitor chemical reactions
• determine the purity of a known substance/identify impurities
• identify how drugs react with eachother and identify the active ingredients

non destructive quick and relaible

Question 7

What is a mass spectrometer?

Answer 7

An instrument used to measure the masses of atoms, molecules and ions that are not available to gravity

Question 8

State

Steps during Mass spectrometry?

Answer 8

1. Evacuation
2. Vapourisation
3. Ionisation
4. Acceleration
5. Deflection
6. Detection

Question 9

Why can’t free radicals be detected in the mass spectrometer

Answer 9

they are not charged so they can not be accelerated or deflected and consequently, not detected

Question 10

Case Study : Chlorine

How are chlorine free radicals formed in the mass spectrometer?

Answer 10

if the high energy electrons are energetic enough, the molecular ion undergoes fragmentation f to form a free radical and a daughter ion

Cl2^+ +e- —> Cl. + Cl^+ + e-