Edexcel International A Level Chemistry
Edexcel International A Level Chemistry Spectroscopy and Chromatography Exam Questions
Free Edexcel International A Level Chemistry exam questions for Spectroscopy and Chromatography, with a mark scheme for every pack. Covers 13C and proton NMR, chemical shift, splitting, integration, TMS, combined spectra, TLC, gas chromatography and HPLC.
Spectroscopy and Chromatography exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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A-Level Chemistry Flashcards for 2027 Onwards
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About Edexcel International A Level Chemistry Spectroscopy and Chromatography
Spectroscopy and chromatography in Unit 4 of Edexcel International A Level Chemistry completes the analytical toolkit begun with Mass spectra and IR in Unit 2. You learn how carbon-13 and proton NMR show the number and type of chemical environments, how chemical shift, integration and splitting patterns reveal structure, and how to combine NMR with mass spectrometry and IR to identify unknown compounds. Chromatography is used to separate and identify the components of mixtures. Examiners frequently provide several spectra and ask for a full structure, with marks for explaining each piece of evidence, as well as asking about Rf values and retention times.
What you need to know
- 13C NMR Each peak represents a different carbon environment. Chemical shift values from a data sheet indicate the type of carbon, for example C=O in the range of about 160 to 220 ppm.
- Proton NMR basics The number of peaks gives the number of hydrogen environments. Relative peak areas (integration) give the ratio of hydrogens in each environment.
- Splitting The n+1 rule: a peak is split into n+1 lines by n hydrogens on adjacent carbons. A CH2CH3 group gives a quartet and a triplet. OH protons usually appear as singlets.
- Standards and solvents TMS, Si(CH3)4, is the reference at 0 ppm because it gives a single strong peak away from most others, and it is inert and volatile. Samples are dissolved in solvents without 1H atoms, such as CDCl3.
- Chromatography Separation depends on the relative affinity of components for a stationary phase and a mobile phase. TLC uses Rf = distance moved by spot / distance moved by solvent.
- GC and HPLC Gas chromatography and high performance liquid chromatography separate components, which are identified by retention time. They can be coupled with mass spectrometry to identify each component.
Common mistakes in Spectroscopy and Chromatography
- Counting hydrogens instead of environments when predicting the number of peaks.
- Applying the n+1 rule to hydrogens on the same carbon. Splitting comes from hydrogens on adjacent carbons.
- Saying TMS is used because it has 12 hydrogens. The key reason is a single peak at a shift away from other peaks, plus being inert.
- Measuring Rf to the edge of the spot or the bottom of the plate. Measure from the baseline to the centre of the spot and to the solvent front.
- Giving a structure without linking each spectral feature to evidence. Mark schemes reward each deduction.
Try three Spectroscopy and Chromatography exam-style questions
1. Predict the proton NMR spectrum of ethyl ethanoate, CH3COOCH2CH3: number of peaks, relative areas and splitting. (3 marks)
Show the mark scheme answer
Three peaks; areas 3 : 2 : 3; CH3CO singlet, OCH2 quartet, CH2CH3 triplet.
2. How many peaks would be seen in the 13C NMR spectrum of propan-2-ol, (CH3)2CHOH? Explain. (2 marks)
Show the mark scheme answer
Two peaks; the two CH3 carbons are in the same environment, and the CH carbon bonded to OH is a different environment.
3. In a TLC experiment a spot moves 3.6 cm and the solvent front moves 8.0 cm. Calculate the Rf value. (1 mark)
Show the mark scheme answer
Rf = 3.6 / 8.0 = 0.45.
Spectroscopy and Chromatography FAQs
What does Edexcel International A Level Chemistry Spectroscopy and chromatography cover?
It covers 13C and proton NMR (chemical shift, integration, splitting and TMS), combining spectra to deduce structures, and TLC, gas chromatography and HPLC for separating and identifying mixtures.
Which unit is Spectroscopy and chromatography examined in?
It is part of Unit 4, but structure determination questions can combine it with mass spectra and IR from Unit 2.
How do I approach a combined spectra question?
Use the mass spectrum for Mr, IR for functional groups, 13C NMR for carbon environments and proton NMR for hydrogen environments, then propose a structure and check it against every piece of data.
