Study Notes
Mass spectrometry is an analytical technique used to identify unknown substances by analyzing the mass-to-charge ratio of ions. It involves bombarding molecules with high-energy electrons to create positively charged ions, which are then sorted by their mass-to-charge ratio in a detector. The resulting mass spectrum can be used to determine isotopic abundances, calculate relative atomic masses, and deduce molecular formulas.
Exam Tips
Key Definitions to Remember
- Mass-to-charge ratio (m/e): The ratio of the mass of an ion to its charge.
- Isotopes: Atoms of the same element with different numbers of neutrons.
- Relative atomic mass (Ar): The average mass of an element's isotopes, weighted by abundance.
Common Confusions
- Confusing the base peak with the molecular ion peak.
- Misinterpreting the M+1 and M+2 peaks for different elements.
Typical Exam Questions
- How do you calculate the relative atomic mass of an element from its isotopic abundances? Use the formula: sum of (isotope mass x relative abundance) / 100.
- What does the M+1 peak indicate in a mass spectrum? It indicates the presence of carbon-13 isotopes.
- How can you identify the presence of bromine or chlorine in a compound using mass spectrometry? Look for the M+2 peak in the mass spectrum.
What Examiners Usually Test
- Ability to interpret mass spectra and identify isotopes.
- Understanding of how to calculate relative atomic mass from isotopic data.
- Knowledge of fragmentation patterns and their significance in identifying molecular structures.