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Colorimetry & Complex Ions (AQA A Level Chemistry): Revision Note

Exam code: 7405

Stewart Hird

Written by: Stewart Hird

Reviewed by: Caroline Carroll

Updated on

Colorimetry & Complex Ions

Colorimetry & Complex Ions

  • Colorimetry can be used to measure the absorption of radiation using a colorimeter

  • This uses a lamp as a source of white light, which passes through a filter to produce light of one colour

    • This colour will be the one that the sample will absorb the most and is called its complementary colour

  • For example hexaaquacopper(II) solution is a pale blue colour which absorbs red light

  • It's complementary colour is blue which is what is transmitted

A simple diagram representing the component parts involved in colorimetry

Worked Example

Outline a practical method for the preparation of an unknown concentration of metal aqua ion solution by colorimetry.

Answer:

  • Make up metal aqua ion solutions of known concentrations

  • Measure absorption or transmission

  • Plot a calibration curve (absorbance vs concentration)

  • Measure absorption of unknown

  • Determine concentration of unknown

 

Visible Spectroscopy Calibration Curve, downloadable AS & A Level Chemistry revision notes

Calibration curve from colorimetry results, showing the absorbance of an unknown being used to determine the concentration

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Author
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Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Content Creator

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

Caroline Carroll

Reviewer: Caroline Carroll

Expertise: Head of Content Delivery

Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about delivering high-quality resources to help students achieve their full potential.