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Simulators for Schools is managed by Simulators for the web (Sim4Web),
Simulators for the web (Sim4Web) is a web based browser environment that allows users to perform experiments using virtual apparatus and UV-Vis absorption spectrometer simulators. Sim4Web is held in a secure location that requires a user to register and log onto the web site. Find out more about Sim4Web here.
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UV-Vis Experiment 7: Ultraviolet-Visible Absorption Spectroscopy & Colour in Chemical Solutions
Why are leaves green, why are carrots and some fizzy drinks orange, why are
certain transition metal complexes highly coloured?
This experiment answers these questions, teaching students the basics of
UV-Vis absorption spectroscopy at the same time.
These exercises are aimed at post 16 students: in schools, colleges and universities
(foundation level/ year 1). Let your students have the opportunity to run their own
spectra & operate a UV-Vis absorption spectrometer simulator!
We look at the relationship between absorbance spectra and the colour
that is perceived of the sample solution
by using the colour wheel.
Several examples will be studied in this experiment: firstly, the absorption spectra
of simple dyes and food dyes will be recorded to gain experience in operating the absorption spectrometer simulator. Students will predict the colour of the dye solution from its absorption spectrum.
Students then have practice at preparing solutions accurately, performing dilutions by using the virtual flask. Samples to be prepared include copper sulphate.
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Transition metal complexes will be
examined with chromium (iii) as
the metal centre. The relationship
between the colour of the sample and
electronic structure will be investigated.
How the type of ligand can affect the colour of a complex is also covered.
Students will build up their own spectrochemical series by running spectra of various
chromium (iii) solutions and making observations. They will calculate the Crystal Field
Stabilisation Energy for each sample from it’s spectrum.
The Beer-Lambert Law is introduced in the
final exercise which relates the absorbance to the concentration of the sample. Students will make up a series of solutions of chromium
nitrate and measure the absorbance spectra. A Beer-Lambert plot will be constructed.
Supervisors can allocate a chromium nitrate solution of unknown concentration. The students can determine the concentration of the unknown
sample from their Beer-Lambert plot.
A detailed experimental procedure guides the students through the tasks in the experiment in addition to providing instruction on how to use the spectrometer simulator and the virtual flask (extract shown):
Students can work their way through the support notes describing the basics of UV-Vis absorption spectroscopy as they progress through the experiment (extract shown).
Students gain experience of running absorption spectra by using the simulator to control the wavelength range, scanning speed and mode of operation (either absorbance or transmittance) – it’s just like using the real thing!
Pay per laboratory session. We also offer very attractive discounts for multiple session purchases. Contact us for more information.
Not ready to register yet? Check out our Demo Site! Login here and simply use firstname.lastname@example.org and password: “demoonly”.
Any questions? Please contact our experts who will be happy to help.
Tried UV-Vis absorption Experiment 7 and enjoyed the experience? Do you have gifted students who enjoy a challenge? Then why not check out the rest of our catalogue of UV-Vis experiments here.