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FDSN 507 Midterm 2

Spectroscopy

Define spectroscopy. The study of the interaction between electromagnetic radiation and matter; measure different wavelengths of light.
What three things does spectroscopy include? Absorption, emission, diffraction
Name four different kinds of spectroscopy. IR, UV-Vis, Fluorescence, NMR
T or F: Light have wave-like properties. True
_____ represents the distance between successive maxima on any given wave. Wavelength
_____ is the number of occurances of a repeated event per unit time. Frequency
_____ is the magnitude of the electric vector at the wave maxima. Amplitude
Oscillating _____ and _____ fields make up a wave. electric, magnetic
A wave consists of discrete packets f energy called _____. photons
The energy of a photon can be defined in terms of ____ of the wave. frequency
_____ light is electromagnetic radiation composed of waves having a single frequency and wavelength. Monochromatic
T or F: Monochromatic light is obtained by refraction. False
Emitted light has longer _____ and less ____ than absorbed light. wavelength, energy
T or F: Atoms and molecules exist primarily in their excited state. False
T or F: The internal energy constant of a molecule is discrete. True
The relative _____ of an atom corresponds to the energy difference between excited and ground state. potential energy
The ____ range results in transitions between electronic energy levels. UV-Vis
The ____ range results in transitions between vibrational energy levels. IR
Describe the steps in absorption. 1. Energy from electromagnetic radiation is transferred to an atom. 2. Atom goes from ground to excited state. 3. Absorption spectrum is obtained.
Name two ways which a molecule may dissipate energy. Heat, emission of radiation
What are the two types of UV-Vis spectroscopy? Which is qualitative and which is quantitative? Absorbance (qualitative), fluorescence (quantitative)
____ spectroscopy is based on the amount of light absorbed from a reference beam as it passes through a sample solution. Absorbance
T or F: Analyte present in solution will not affect the amount of light transmitted. False
Relative transmittance and absorption are correlated to analyte _____. concentration
T or F: Absorbance is linear with concentration, transmittance is not. True
____ law gives the relationship between absorbance and concentration. Beer's
Define zeroing. A reference cell is used to correct for loss due to scattering and reflection.
What three conditions might cause deviations from Beer's law? Analyte concentration is > 10 mM, chemical processingcause dissociation of molecules, polychromatic light causes different absorptivity.
Quartz and fused silica holding cells are used for ____ spectroscopy. UV
Silicate plates and plastic cells are used for ___ spectroscopy. Vis
What should be considered procedurally for spectroscopy? Sample prep, selection of appropriate wavelength, calibration of the instrument.
T or F: A linear calibration curve obeys Beer's law. True
Why might a calibration curve be non linear? Absorbance per change in concentration is not constant, limitations in instrument.
Calibration of UV-Vis requires a _____ protocol. standard addition
T or F: High relative errors result with measurements of intermediate transmittance. False
Describe fluorescence spectroscopy. The signal measured is the electromagnetic radiation emitted from the analyte.
T or F: The optimum radiation wavelength for fluorescence spectroscopy is during excitation and a shorter wavelength during emission. False
Created by: goberoi
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