Advanced Placement (AP) Chemistry Practice Exam

What is the purpose of mass spectrometry in chemistry?

1. To measure the volume of gases at standard conditions

2. To create a mass spectrum graph of various isotopic elements

3. To determine the empirical formula of a compound

4. To evaluate ionization energy

The correct answer is: To create a mass spectrum graph of various isotopic elements

Mass spectrometry is a powerful analytical technique used to measure the masses of particles, allowing for the identification and quantification of different isotopes and chemical species within a sample. The technique works by ionizing chemical species and sorting the resulting ions based on their mass-to-charge ratio. The primary purpose of mass spectrometry is indeed to create a mass spectrum, which is a graphical representation of the different ions detected, plotted against their mass-to-charge ratios. This spectrum provides valuable information about the isotopic composition of elements present in the sample, allowing chemists to identify the types of chemical species and their abundances. Each peak in the mass spectrum corresponds to a specific ion, and the height of each peak indicates the relative abundance of that ion compared to others. This technique is essential in various fields such as biochemistry, environmental science, and forensic science for analyzing complex mixtures and determining molecular structures. While mass spectrometry may indirectly contribute to empirical formula determination or provide insights related to ionization energy, its main function centers on generating these detailed mass spectra for analysis.