Techniques that make use the interactions of matter and electromagnetic radiation are critically important to the qualitative analysis of chemical substances. The most important techniques of molecular spectroscopy in the modern laboratory are infrared, NMR, ultraviolet, and mass spectroscopy. (With mass spectroscopy, the 'spectrum' refers to a distribution of ions sorted by weight.)
For the MCAT, firstly. you need to have a solid physical sciences understanding of the basis for how the techniques work. Secondly you need to have in hand the half dozen or so guideposts for basic interpretation of results within each method. Types of problems involving identification of an unknown on the MCAT are typically straightforward.
Molecular Spectroscopy Images
Conceptual Vocabulary Self-Test
Basic Terms Crossword Puzzle
Basic Puzzle Solution
Conceptual Vocabulary for Molecular Spectroscopy