Question detail
In mass spectrometry, what does the molecular ion peak represent?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Organic analysis
Question
- A. The most abundant fragment of the molecule
- B. The molecular weight of the intact molecule
- C. The presence of functional groups
- D. The average mass of all isotopes
Answer
The molecular weight of the intact molecule
Explanation
The molecular ion peak in a mass spectrum corresponds to the intact molecule's mass-to-charge ratio (m/z). This evidence indicates the molecular weight of the compound being analyzed. The implication is that by identifying this peak, chemists can ascertain the molecular formula of the substance. Thus, the molecular ion peak is essential for determining the molecular weight of a compound.
Common mistake
Misunderstanding Fragmentation Patterns
Students often misinterpret the fragmentation patterns in mass spectra, confusing the peaks with the molecular ion peak.
To fix this, students should focus on identifying the highest m/z value peak as the molecular ion peak and analyze the lower m/z peaks as fragments that provide information about the structure.
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