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SingaporeChemistry

Analytical Techniques

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does carbon-13 NMR reveal the number and types of carbon environments in a molecule?

Interpret a carbon-13 NMR spectrum by relating the number of peaks to the number of carbon environments and the chemical shift of each peak to the type of carbon environment using the data booklet
A focused answer to the H2 Chemistry learning outcome on carbon-13 NMR. Why carbon-13 is observed, relating the number of peaks to the number of carbon environments, and using the data-booklet chemical shift ranges to assign each carbon, including its complementary role to proton NMR.
7 min answer →

How are common cations, anions and gases identified by simple chemical tests in qualitative analysis?

Describe the chemical tests used in qualitative analysis to identify common cations (including with NaOH and aqueous ammonia), anions (carbonate, sulfate, halides, nitrate) and gases, and interpret the observations
A focused answer to the H2 Chemistry learning outcome on qualitative analysis. Tests for common cations with sodium hydroxide and aqueous ammonia, tests for carbonate, sulfate, halide and nitrate anions, and the standard gas tests, with the observations expected in Paper 4.
9 min answer →

How does infrared spectroscopy identify the functional groups present in an organic molecule?

Explain the origin of infrared absorption from bond vibrations, use characteristic absorption ranges from the data booklet to identify functional groups, and distinguish compounds such as alcohols, carbonyls and carboxylic acids from their spectra
A focused answer to the H2 Chemistry learning outcome on infrared spectroscopy. The origin of IR absorption in bond vibrations, using the data-booklet absorption ranges to identify functional groups, and distinguishing alcohols, carbonyls and carboxylic acids from their characteristic absorptions.
8 min answer →

How does mass spectrometry reveal relative molecular mass and structural fragments of an organic compound?

Interpret a mass spectrum to identify the molecular ion and relative molecular mass, deduce fragments from peaks, and explain isotope patterns including the M+2 peak of chlorine and bromine compounds
A focused answer to the H2 Chemistry learning outcome on mass spectrometry. Identifying the molecular ion and relative molecular mass, deducing common fragments from mass differences, and interpreting isotope patterns such as the characteristic M and M+2 peaks of chlorine and bromine compounds.
8 min answer →

How does proton NMR spectroscopy reveal the number, environment and neighbours of hydrogen atoms in a molecule?

Interpret a proton (1H) NMR spectrum using chemical shift, peak area (integration), and spin-spin splitting (the n+1 rule), and use D2O exchange to identify OH and NH protons
A focused answer to the H2 Chemistry learning outcome on proton NMR. Using chemical shift to identify the proton environment, integration (peak area) for the number of protons, the n+1 splitting rule for neighbouring protons, and D2O exchange to spot OH and NH protons.
10 min answer →

How are mass spectrometry, infrared and NMR data combined with chemical tests to deduce the full structure of an unknown organic compound?

Combine evidence from mass spectrometry, infrared spectroscopy, proton and carbon-13 NMR and chemical tests to deduce the structure of an organic compound, working systematically from molecular mass to functional groups to the carbon skeleton
A focused answer to the H2 Chemistry learning outcome on combined structure determination. A systematic strategy for using mass spectrometry, infrared, proton and carbon-13 NMR and chemical tests together to deduce an unknown organic structure, with a fully worked multi-technique example.
10 min answer →