Edexcel A-Level Chemistry 9CH0
Atomic Structure and the Periodic Table
Bonding and Structure
Inorganic Chemistry and the Periodic Table
Formulae, Equations and Amounts of Substance
Organic Chemistry I
Modern Analytical Techniques I
Energetics I
Kinetics I
Equilibrium I
Acid-Base Equilibria
Energetics II
Redox II
Transition Metals
Kinetics II
Organic Chemistry II
Organic Chemistry III
Modern Analytical Techniques I
- 3 subtopics
- 9 things to know
- Papers 2 and 3
What Modern Analytical Techniques I covers
Covers what a mass spectrum reveals about a molecule and how infrared absorptions identify functional groups.
Where it is assessed
Papers 2 and 3
Advanced Organic and Physical Chemistry, then the synoptic paper.
Check the Pearson Edexcel specification ↗The 3 subtopics
Each one has its own page.
- Mass spectrometryThe molecular ion peak and reading Mᵣ from it, why isotope peaks can sit at higher m/z, how fragmentation arises and why only positive fragments are detected, the groups lost at 15, 17, 29 and 45, and calculating mass lost to propose a structure.Open →
- Infrared spectroscopy and the characteristic absorptionsHow infrared absorptions at characteristic wavenumbers identify functional groups, the C–H, C=C, O–H, C=O and N–H absorptions, why O–H peaks are broad and broader still in carboxylic acids, and telling primary from secondary amines by their N–H peaks.Open →
- Deducing functional groups from an infrared spectrumThe steps for deducing the functional groups in an unknown from its infrared spectrum and for predicting the spectrum of a known compound, the test-tube tests used in Core Practical 7, and telling a ketone from an alcohol by its C=O and O–H absorptions.Open →
What you need to know
Answer each one before you reveal it.
What can a mass spectrum tell you about a compound?
In a mass spectrum, a loss of 15 mass units from the molecular ion indicates the loss of which group?
How does the O–H absorption in carboxylic acids differ from that in alcohols?
What analytical technique is used in Core Practical 7 to help identify unknown organic compounds?
What is the first step when using IR spectroscopy to identify an unknown compound?
What does the molecular ion peak (M⁺) in a mass spectrum represent?
What is the purpose of infrared spectroscopy in organic chemistry?
After obtaining an IR spectrum of an unknown compound, what should you do next?
Take Modern Analytical Techniques I further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Molecular ion peak vs Fragment ion peak
Molecular ion peak: signal corresponding to the intact ionised molecule. Fragment ion peak: signal corresponding to a charged piece after bond breaking.
Infrared spectroscopy vs Mass spectrometry
Infrared spectroscopy: analysis using absorption caused by bond vibrations. Mass spectrometry: analysis using mass-to-charge ratios of ionised particles.
Questions from this topic
Each one with the model answer underneath.
- 1
What does the molecular ion peak (M⁺) in a mass spectrum represent?
Model answer
The intact molecule that has lost one electron.
- 2
What does the molecular ion peak tell you about Mᵣ?
Model answer
Take the m/z at the molecular ion peak; that value is Mᵣ.
- 3
How is an organic compound's relative molecular mass read off a mass spectrum?
Model answer
Read the m/z value of the molecular ion peak, which is typically the peak at highest m/z (excluding isotope peaks).
- 4
Why might the molecular ion peak not be the absolute highest m/z peak in a mass spectrum?
Model answer
Because isotope peaks (such as those containing ¹³C) may appear at slightly higher m/z values than the main molecular ion peak.
- 5
Explain how fragmentation patterns arise in mass spectrometry.
Model answer
The molecular ion breaks apart into smaller positively charged fragments and neutral species.
- 6
Why do only some fragments from the molecular ion appear as peaks in the mass spectrum?
Model answer
Only positively charged fragments are detected; neutral species are not recorded.
What is inside Levo
Six ways to work the same material.
Modern Analytical Techniques I revision questions
- What does Modern Analytical Techniques I cover in Edexcel A-Level Chemistry?
- 3 subtopics: mass spectrometry, infrared spectroscopy and the characteristic absorptions and deducing functional groups from an infrared spectrum. Each one has its own page with questions and model answers.
- How is Modern Analytical Techniques I organised?
- By the Edexcel 9CH0 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Modern Analytical Techniques I, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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