Colourful Solutions > Practical Scheme of Work > E402 - Determination of copper by colourimetry

IB Chemistry Shop

Standard level

Colourimetry is an analytical method that depends on the absorbance of light of a specific wavelength or waveband.


Background

Copper(II) compounds are blue in colour due to the copper hexaaqua complex ion, [Cu(H2O)6]2+

The blue colour means that the aqueous copper ions absorb more light in the orange part of the electromagnetic spectrum than in other regions. This can be shown using the complementary colour wheel that is in the chemistry databooklet.

The complementary colour wheel

The absorbance of electromagnetic radiation follows the Beer-Lambert law, where:

Absorbance = ecl

The molar absorption coefficient depends on both the absorbing species and the wavelength/waveband used.

This problem can be overcome by the use of a calibration curve prepared using known concentrations of the absorbing ion.


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Requirements

Chemicals

Apparatus


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Procedure


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