HSC Chemistry — Module 8
Spectroscopy — Flashcards & Quiz
Spectroscopy lets chemists identify unknown compounds from the way they interact with electromagnetic radiation, and HSC Chemistry Module 8 tests your fluency in mass spectrometry, infrared, proton NMR and UV-Vis. You need to read characteristic peaks, link IR stretches to functional groups, count proton environments in NMR, and combine multiple techniques to propose a structure — the flagship Module 8 extended-response question.
Sample Flashcards
Q1: What is atomic absorption spectroscopy (AAS)?
AAS measures the concentration of specific metal ions in a sample. The sample is atomised in a flame, and a light beam of a specific wavelength (matching the target element) is passed through. Atoms absorb this light. Greater absorption = higher concentration. Beer-Lambert law relates absorption to concentration.
Q2: How does mass spectrometry work?
A mass spectrometer: 1) Vaporises the sample. 2) Ionises molecules (electron bombardment). 3) Accelerates ions through an electric field. 4) Deflects ions with a magnetic field (lighter ions deflect more). 5) Detects ions. The mass spectrum shows m/z (mass-to-charge) ratio vs relative abundance. Used to determine molecular mass and structure.
Q3: What information does infrared (IR) spectroscopy provide?
IR spectroscopy identifies functional groups in organic molecules. Different bonds absorb IR radiation at characteristic frequencies (wavenumbers). The IR spectrum shows absorption peaks that correspond to bond vibrations (stretching, bending). Used to identify functional groups like -OH, C=O, N-H, C-H.
Q4: What is UV-visible spectroscopy used for?
UV-visible spectroscopy measures the absorption of UV and visible light by a sample. Coloured solutions absorb complementary wavelengths. Used to determine concentration (Beer-Lambert law: A = εcl) and identify coloured compounds. A calibration curve of absorbance vs concentration allows unknown concentrations to be determined.
Q5: Compare the information provided by different spectroscopic techniques.
Mass spectrometry: molecular mass and structure (fragmentation pattern). IR spectroscopy: functional groups present. UV-vis spectroscopy: concentration (Beer-Lambert) and electronic transitions. AAS: concentration of specific metal ions. NMR: hydrogen/carbon environments in molecules.
Sample Quiz Questions
Q1: AAS can measure multiple elements simultaneously.
Answer: FALSE
AAS typically measures ONE element at a time, using a specific hollow cathode lamp for each element.
Q2: In a mass spectrometer, heavier ions are deflected more than lighter ions.
Answer: FALSE
LIGHTER ions are deflected MORE because they have less momentum. Heavier ions travel in wider arcs (less deflection).
Q3: IR spectroscopy identifies functional groups in organic molecules.
Answer: TRUE
Different functional groups absorb IR radiation at characteristic frequencies, producing unique absorption peaks in the IR spectrum.
Related Concepts
Last updated: March 2026 · 5 flashcards · 5 quiz questions