Unit Overview
Introduction to analytical chemistry
CIE A-Level ChemistryΒ· 5 min read π n/a
1. Unit at a glance
This unit moves beyond traditional physical property testing to the instrumental and experimental analytical methods used in modern chemistry. You will learn three core techniques in sequence, each building on your understanding of molecular properties to solve compound identification problems.
All sub-topics in this unit are listed below:
Mass spectrometry
Learn how mass spectrometry calculates molecular mass and identifies molecular formulas of compounds.
β β β± 10 min
Infra-red spectroscopy
Understand how IR absorption is used to identify common functional groups in organic molecules.
β β β± 12 min
Chromatography basics
Explore mixture separation principles and calculate Rf values to identify mixture components.
β β± 10 min
2. Common Pitfalls
Wrong move:
Confusing the molecular ion peak with the base peak in mass spectrometry.
Why:
The highest intensity peak is not always the peak corresponding to the full molecule's mass.
Correct move:
The molecular ion peak is the peak with the highest significant m/z value (ignoring small isotope peaks).
Wrong move:
Assigning any IR absorption to a functional group without checking the wavenumber range.
Why:
All bonds absorb IR, but only specific ranges correspond to characteristic functional group absorptions.
Correct move:
Always cross-reference your observed peak against the standard wavenumber table for assignments.
3. Quick Reference Cheatsheet
Key Concept / Formula | Summary |
|---|---|
Molecular ion peak () | Gives the relative molecular mass of the analyte compound |
Base peak (mass spectrometry) | The peak with 100% relative intensity, the most abundant fragment ion |
IR absorption principle | Bond vibration absorbs specific IR wavenumbers unique to each bond type |
value (chromatography) | |
Stationary phase | Retains solutes via adsorption or partitioning, enabling mixture separation |
What's Next
Begin this unit by studying the first core technique, mass spectrometry, to learn how it is used to find molecular mass. Once you complete all three sub-topics in this unit, you can move on to the next unit covering organic synthesis.