Intro to Spectroscopy (UV-Vis, IR) - Problem Set
Q. In UV-Vis spectroscopy, what does a higher absorbance value indicate?
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A.
Lower concentration of the analyte
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B.
Higher concentration of the analyte
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C.
Higher wavelength of light
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D.
Lower path length of the sample
Solution
A higher absorbance value indicates a higher concentration of the analyte, according to Beer-Lambert law.
Correct Answer: B — Higher concentration of the analyte
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Q. What does a broad peak in an IR spectrum typically indicate?
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A.
Strong hydrogen bonding
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B.
Weak molecular interactions
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C.
High molecular weight
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D.
Low concentration
Solution
A broad peak in an IR spectrum often indicates strong hydrogen bonding, which causes a range of vibrational frequencies.
Correct Answer: A — Strong hydrogen bonding
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Q. What is the main advantage of using a Fourier Transform Infrared (FTIR) spectrometer over a traditional IR spectrometer?
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A.
Higher resolution
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B.
Faster data acquisition
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C.
Lower cost
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D.
Simpler operation
Solution
FTIR spectrometers offer faster data acquisition and higher resolution due to their ability to collect all wavelengths simultaneously.
Correct Answer: B — Faster data acquisition
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Q. What is the typical range of wavelengths for UV-Vis spectroscopy?
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A.
100-400 nm
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B.
400-800 nm
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C.
200-800 nm
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D.
800-2500 nm
Solution
The typical range for UV-Vis spectroscopy is 200-800 nm, covering both ultraviolet and visible light.
Correct Answer: C — 200-800 nm
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Q. What type of molecular vibrations are primarily observed in IR spectroscopy?
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A.
Rotational transitions
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B.
Electronic transitions
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C.
Vibrational transitions
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D.
Nuclear transitions
Solution
IR spectroscopy primarily observes vibrational transitions of molecules, which occur when bonds stretch or bend.
Correct Answer: C — Vibrational transitions
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Q. Which instrument is commonly used to measure IR spectra?
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A.
Spectrophotometer
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B.
Chromatograph
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C.
Mass spectrometer
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D.
NMR spectrometer
Solution
An IR spectrophotometer is the instrument commonly used to measure infrared spectra.
Correct Answer: A — Spectrophotometer
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Q. Which type of bond is most commonly analyzed using IR spectroscopy?
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A.
C-H bonds
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B.
C-C bonds
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C.
N-H bonds
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D.
O-H bonds
Solution
C-H bonds are commonly analyzed using IR spectroscopy, as they produce strong and distinct absorption peaks.
Correct Answer: A — C-H bonds
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