Modern Analytical Techniques I | Edexcel A-Level Chemistry (9CH0)
Modern Analytical Techniques I
- 45 questions
- 3 subtopics
- Paper 2: advanced organic and physical chemistry
- Paper 2 and Paper 3
Covers what a mass spectrum reveals about a molecule and how infrared absorptions identify functional groups..
It covers mass spectrometry, infrared spectroscopy and the characteristic absorptions and deducing functional groups from an infrared spectrum.
Sample questions from Modern Analytical Techniques I
Answer each one closed book first, then open the answer.
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Mass spectrometry
In a mass spectrum, a loss of 15 mass units from the molecular ion indicates the loss of which group?
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CH₃ (a methyl group). -
Mass spectrometry
What does the term m/z represent in mass spectrometry?
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The mass-to-charge ratio of an ion. -
Infrared spectroscopy and the characteristic absorptions
What type of peak does C=C stretching in alkenes produce in an IR spectrum?
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A characteristic absorption peak at a specific wavenumber range. -
Infrared spectroscopy and the characteristic absorptions
How does the O–H absorption in carboxylic acids differ from that in alcohols?
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The O–H absorption in carboxylic acids is characteristically very broad, extending over a wide wavenumber range, due to stronger hydrogen bonding. -
Deducing functional groups from an infrared spectrum
What is the final step in deducing the functional groups present in an unknown compound from its IR spectrum?
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Deduce which functional groups are present based on matches between observed peaks and reference wavenumber data. -
Deducing functional groups from an infrared spectrum
What can you predict about an IR spectrum once you know the characteristic wavenumber ranges for the functional groups in a compound?
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You can predict which absorption peaks will appear in the IR spectrum and at approximately which wavenumbers.
The 3 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Mass spectrometry | The 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. | 20 |
| Infrared spectroscopy and the characteristic absorptions | How 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. | 16 |
| Deducing functional groups from an infrared spectrum | The 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. | 9 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
Edexcel A-Level Chemistry Active Recall Guide
Every topic, not just this one. 1,534 questions with their answers.