Colourimetry Tutorial 2021W1 CHEM 154 Online Labs.pdf -...

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Colourimetry Tutorial
This tutorial is intended as instruction for the Beer's Law technique used in Exp. 11. This tutorial deals
with the following principles of colourimetry:
Why use colourimetry?
How does colourimetry work?
Proper experimental technique
Introduction
Why Use Colourimetry?
Colourimetry can yield a wealth of information on coloured solutions. It is a quick and non-destructive
method that can identify solutes in a solution and very accurately determine their concentrations.
Computer technology has automated the somewhat tedious calculations required for colourimetric
analysis and now allows colourimetry experiments to be performed within the span of a few minutes
from start to finish.
In short, a colourimetric analysis is straightforward, relatively foolproof, and highly informative.
How Does Colourimetry Work?
Colourimetry is a form of spectroscopy , an analysis that measures how atoms or molecules respond
when exposed to electromagnetic radiation of a certain wavelength, and therefore, of a certain
energy. In a way, colourimetry is the most familiar kind of spectroscopy, because the wavelengths
used are from the visible light region of the electromagnetic spectrum.
The electromagnetic spectrum; note the visible light region in the middle. Radiation from this region is
used in colourimetry. Illustration from NASA
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The relation of a wave's energy, E, to its wavelength, the Greek letter lambda. Energy is inversely
proportional to wavelength.