‹ Chemistry simulationsChemistry · AS Level 9701 · 22 Analytical techniquesFive simulations covering Topic 22: why some bond vibrations absorb infrared and others do not, with the dipole drawn on the vibrating molecule; an infrared spectrum you can read peak by peak against the Data Booklet ranges; two spectra side by side so you can see which band tells the compounds apart; a mass spectrum with the molecular ion, the fragments and the M+1 peak that counts the carbons; and the M+2 patterns that give away chlorine and bromine.
Every bond vibrates, stretching and bending at a frequency set by the bond strength and the masses of the atoms. Infrared radiation of exactly that frequency is absorbed, but only if the vibration changes the dipole moment of the molecule. Pick a molecule and a vibration, watch the dipole arrow, and see which ones a spectrometer can detect.
A spectrometer shines infrared through a sample and plots how much gets through at each wavenumber. Every dip is a bond absorbing. Hover over a dip to name it, click to keep the label, and switch on the Data Booklet ranges to see how a chemist matches a dip to a functional group.
The usual exam question gives two spectra, or two candidate structures, and asks which absorption settles it. Pick a pair and the two spectra are drawn one above the other with the deciding absorptions picked out. Some pairs are easy; one of them cannot be separated by infrared alone.
In a mass spectrometer the molecule loses an electron to become the molecular ion, M+, and many of those ions then break into fragments. The peak at the highest m/z gives the relative molecular mass, the fragments show how the molecule was put together, and the tiny M+1 peak counts the carbon atoms. Click any bar to identify it.
Chlorine is three parts 35Cl to one part 37Cl, and bromine is half 79Br and half 81Br. Any ion containing a halogen therefore appears as a cluster of peaks two mass units apart, and the heights of the cluster say how many halogen atoms are present. Pick a compound, then read the probability grid that builds the ratio.
Five interactive simulations for Cambridge AS Level Chemistry 9701 topic 22 Analytical techniques: HCl, CO2, water and nitrogen vibrating in 3D with the dipole moment drawn so you can see which vibrations absorb infrared, an infrared spectrum plotter for seven organic compounds with every peak named and the Data Booklet wavenumber ranges overlaid, a side-by-side comparison that shows which absorption distinguishes an alcohol from an acid or an ester, a mass spectrum builder with the molecular ion, the main fragments and the M+1 peak used to count carbons, and the M+2 and M+4 isotope patterns for chlorine and bromine compounds explained with the probabilities.
Five simulations covering Topic 22: why some bond vibrations absorb infrared and others do not, with the dipole drawn on the vibrating molecule; an infrared spectrum you can read peak by peak against the Data Booklet ranges; two spectra side by side so you can see which band tells the compounds apart; a mass spectrum with the molecular ion, the fragments and the M+1 peak that counts the carbons; and the M+2 patterns that give away chlorine and bromine.
Analytical techniques is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 22 Analytical techniques). The course is assessed in Paper 1 (Multiple Choice (AS)), Paper 2 (AS Structured), Paper 3 (Advanced Practical), Paper 4 (A Level Structured), Paper 5 (Planning, Analysis, Evaluation). Syllabus for examination in 2025-2027. There are 5 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.
Full syllabus map: AS Level Chemistry 9701 topic 22.
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