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VCE Chemistry
Unit 3 2013Chapter 7 UV-Visible Spectroscopy
Week commencing 18th FebMs Lennard
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Overview
Chapter 7 spectroscopy
The electromagnetic spectrum
UV-visible spectroscopy Theory for SAC Prac #1 Determination of the
P content of lawn food
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Chapter 7 - spectroscopy
We will study AA after we have completed
theory for the 1st SAC (EEI)
We will complete and IR, NMR after we have
completed Chapter 9 (organic chemistry)
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keywords
Electromagnetic spectrum UV (ultra violet) visible spectroscopy
Colorimetry (visible spectroscopy)
Calibration curve
Monochromator
Absorbance
Transmittance
Spectrum
photon
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wavelength
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Electromagnetic spectrum
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Electromagnetic spectrum
http://www.youtube.com/watch?v=kfS5Qn0w
n2o
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spectroscopy
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UV-Visible spectroscopy
Measures the light absorbed by substances as
their electrons jump to higher energy levels
The colour of a solution is the result of the
light transmitted by that solution after certain
components of visible light have been
absorbed through electron transitions
A coloured substance absorbs its complementary
colour eg. A solution appears yellow because the
blue and violet light has been absorbed and the
transmitted light is yellow
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UV-Visible spectroscopy
The position of a peak in a UV-vis spectrum shows
the energy of the light most strongly absorbed by
that substance
The amount of light absorbed is directly proportionalto the concentration of the compound
A calibration curve (generated from the
absorbance of samples of known concentration) is
used to determine the concentration of the
compound
UV-vis spectroscopy is used to determine
concentration of solutions of coloured compounds
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Beer - Lambert Law
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Visible light and complementary colours
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Visible light
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UV - vis
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UV- vis spectrophotometer
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faculty.sdmiramar.edu
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www.snypa.co.uk/OSR/UV/Resources/UV_spec.jpg
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http://www.youtube.com/watch?v
=0n-dbLzj_HM
You tube UV/Vis Spectroscopy
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Visible spectrum of the green pigment chlorophyll
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Using UV-Vis spectrum to choose the wavelength for analysis
choose a wavelength where the substance absorbs strongly
eg. 420nm or 660nm
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Calibration curves Enable unknown concentrations to be determined by
comparing with known standards (of concentration)
A series of standard solutions are tested using the
equipment under the same conditions
The response to these standards is measured andplotted to form a calibration curve (which is usually a
straight line)
The measurement of the unknown sample is plottedon the same curve and its position is used to find its
concentration
Calibration curves are used in AA and UV-Vis
spectroscopy
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Calibration curves
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Worked example 7.4 p. 87
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Worked example 7.4 p. 87
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Questions p. 88
Q6, 7, 9, 10, 11, 12
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2008 June Exam
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2008 June Exam
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2008 June Exam
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2008 June Exam
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2008 June Exam
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