Chemistry AQA AS Unit 2 Analytical Techniques

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created on: 02-09-13 13:29
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Analytical Techniques
Used to measure the relative atomic masses of atoms/molecular mass of organic
Molecular ions will break up, and some of their bonds break as being ionised. This is called
FRAGMENTATION. Each of these give off a different peaks.
However there are normally a few ionised molecules remaining intact to give a peak
corresponding to the Mr.
Can measure masses to ¾ decimal places.
Often used by organic chemists to help them identify compounds.
A pair of atoms joined by a chemical bond is always vibrating.
Stronger bonds vibrate faster (higher frequency), heavier atoms make the bond vibrate
more slowly (lower frequency)
The frequencies are within infra-red electromagnetic spectrum.
The bonds absorb the infra-red radiation that is the same as the natural frequency of the
bond (corresponds to each other).
1. A beam of heat (infra red) passes through the species.
2. The radiation that emerges is missing frequencies that correspond to the types of bonds
found in the sample.
3. Instrument then plots a graph of the intensity of the radiation emerging from the sample,
called the TRANSMITTANCE, against the frequency of radiation.
4. The frequency is expressed as a wave number, measured in cm1.
Infra-red spectrum usually has many peaks.
Each spectrum is as unique as a fingerprint.
Can also identify impurities.


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