A Level Chemistry OCR Practice Exam

In mass spectrometry, what occurs during the fragmentation process?

1. A molecule absorbs energy and becomes ionized

2. A positive ion splits into smaller ions

3. The ionization results in the release of energy

4. A molecule forms larger, more complex ions

The correct answer is: A positive ion splits into smaller ions

During the fragmentation process in mass spectrometry, a positive ion indeed splits into smaller ions. This process occurs after the initial ionization of the molecule. When a molecule is ionized, it can absorb energy, which can lead to the breaking of chemical bonds within the ionized molecule. As a result, the original ion can fragment into smaller ions and neutral fragments, which can be detected and analyzed by the mass spectrometer. The smaller ions produced during fragmentation are crucial for interpreting the structure of the original molecule because their masses and abundance can provide insights into the molecular structure and the various functional groups present. Each ion will have a specific mass-to-charge ratio (m/z) that can be measured, allowing chemists to deduce information about the molecular composition and fragmentation patterns. This process is essential for identifying and characterizing unknown substances in various applications, from pharmaceuticals to environmental science. While ionization itself involves the absorption of energy, which is often seen in option A, it is the subsequent fragmentation that yields smaller ions, making option B the correct choice. Option C refers to energy release, which is not the focus during the fragmentation stage. Option D implies an increase in complexity, which contradicts the nature of fragmentation, where larger ions break apart