# A food scientist analyses a sample of a flavouring compound using mass spectrometry and infrared spectroscopy. The mass spectrum shows a molecular ion peak at m/z = 88. The infrared spectrum shows a broad absorption between 2500–3300 cm⁻¹ and a strong absorption at approximately 1710 cm⁻¹. Explain how these two techniques together allow the food scientist to identify the flavouring compound.

> Edexcel A-Level Chemistry (9CH0) — 7.1 Mass spectrometry and infrared · Explain · 5 marks

> Mass spectrometry gives the relative molecular mass of a compound by detecting the mass-to-charge ratio (m/z) of ions. Infrared spectroscopy identifies functional groups present in a molecule because different chemical bonds absorb infrared radiation at characteristic wavenumbers. A broad absorption between 2500–3300 cm⁻¹ is characteristic of the O–H bond in a carboxylic acid, and a strong absorption at approximately 1710 cm⁻¹ is characteristic of the C=O bond in a carboxylic acid.

## Mark scheme (5 marks)

1. Mass spectrometry gives the relative molecular mass (Mr) of the compound
2. The molecular ion peak at m/z = 88 means the relative molecular mass of the compound is 88
3. Infrared spectroscopy identifies the functional groups present in the compound
4. The absorptions at 2500–3300 cm⁻¹ and 1710 cm⁻¹ indicate the compound contains a carboxylic acid functional group (O–H and C=O bonds)
5. Using both pieces of data together (Mr of 88 and carboxylic acid functional group) allows the scientist to identify the specific compound

## Key terms

- [mass spectrometry](https://www.gradenine.co.uk/glossary/mass-spectrometry)
- [molecular ion peak](https://www.gradenine.co.uk/glossary/molecular-ion-peak)
- [m/z](https://www.gradenine.co.uk/glossary/m-z)
- [infrared spectroscopy](https://www.gradenine.co.uk/glossary/infrared-spectroscopy)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-food-scientist-analyses-a-sample-8cdca4e8) · Published by Druglandscape Ltd.