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Analytical Chemistry Notes

This is a sample of our 11 page long Analytical Chemistry notes, which we sell as part of the IB Chemistry HL Notes collection, a Grade 7 package written at University Of Cambridge in 2012 that contains 57 pages of notes across 8 different documents.

Analytical Chemistry Revision

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Option A: Modern analytical chemistry A1: Analytical techniques A.1.1 State the reasons for using analytical techniques.
- determination of purity
- structure determination
- composition analysis

- separation of mixtures
- identification of substances
- determination of concentration of substance

A.1.2 State that the structure of a compound can be determined by using information from a variety of analytical techniques singularly or in combination.
- combination of analytical techniques used to determine unambiguously the exact structural formula Technique

Uses

IR

- presence of organic functional groups
- strength of bonds

Mass

- structure & relative atomic masses
- isotropic composition of an element

NMR

determine molecular structure (isotopes)

AA

concentration of metal ions in a sample

UV-Vis

test for metal ions

A2: Principles of spectroscopy A.2.1 Describe the electromagnetic spectrum. Microwaves!

Radio waves!

Infrared Radiation!
!

Visible Light!

Ultraviolet Radiation!

X-rays ! Gamma Rays

• Wavelength, λ in units of distance is the distance between successive peaks on the wave.

• Frequency, ƒ in units of Hertz is the number of peaks that pass a fixed point every second.

• All electromagnetic spectrum travel at the same speed in a vacuum (c = 3.00 x 108 m s-1) Velocity of light = frequency x wavelength c = λƒ

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A.2.2 Distinguish between absorption and emission spectra and how each is produced.
- absorption spectroscopy: continuous spectrum with missing regions corresponding to energies absorbed
- energy is required to move/excite electrons from ground state to excited state
- emission spectroscopy: regions corresponding to energies omitted
- radiation emitted by electrons from excited state (higher energy) → ground state (lower energy level)

A.2.3 Describe the atomic and molecular processes in which absorption of energy takes place.
- the greater the energy difference between the levels, the higher the frequency of the light absorbed
- most energetic absorptions = atomic electronic transitions which involve bond breaking + ionization

A3: Infrared (IR) spectroscopy A.3.1 Describe the operating principles of a double-beam IR spectrometer.

S infrared source: produces light M monochromator: produces a single frequency/wavelength A beam splitter: directs half of the radiation through the sample & the other half to the reference D detector: coverts radiation to an electronic signal; compares the intensities of the sample and reference beams; determines the absorption at particular frequencies Why use a reference?
* prevents fluctuations in the output of the source affecting the data
* cancels the effects of the solvent (reference = pure form of the solvent the sample is in)

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