Topic 7: Modern Analytical Techniques I Flashcards
1
Q
How do you find the relative molecular mass of a compound using a mass spectrum?
A
- look at the molecular ion peak (the M peak)
- it has the highest m/z value
- that is the molecular mass
2
Q
How can the molecular ion be broken down?
A
- the bombarding electrons make some of the molecular ions break up into fragments
- these show up, making a fragmentation pattern
- you can use this to identify molecules and their structure
3
Q
How do you work out the structural formula using a mass spectrum?
A
- identify the fragments
- piece them together to form a molecule with the correct molecular mass
4
Q
How can mass spectrometry be used to differentiate between similar molecules?
A
- even if they contain the same atoms, they won’t produce the same set of fragments
5
Q
How does infrared spectroscopy work?
A
- a beam of IR radiation is passed through a sample of a chemical
- the IR radiation is absorbed by the covalent bonds in the molecules, increasing their vibrational energy
- bonds between different atoms absorb different frequencies of IR radiation
- bonds in different places in a molecule absorb different frequencies too
6
Q
How can you show if a reaction has happened using IR spectroscopy?
A
- it is good at telling if a functional group has changed during a reaction
- do some practise qs girlll