Q. In IR spectroscopy, what does a peak at around 1700 cm-1 typically indicate?
A.Presence of alcohols
B.Presence of carbonyl groups
C.Presence of amines
D.Presence of alkenes
Solution
A peak at around 1700 cm-1 in IR spectroscopy typically indicates the presence of carbonyl (C=O) groups, which are characteristic of ketones and aldehydes.
Correct Answer: B — Presence of carbonyl groups
Q. In the context of IR spectroscopy, what does the term 'fingerprint region' refer to?
A.The region above 4000 cm-1
B.The region between 400-1500 cm-1
C.The region below 400 cm-1
D.The region between 1500-2000 cm-1
Solution
The 'fingerprint region' in IR spectroscopy refers to the region between 400-1500 cm-1, where many unique absorption bands occur for different compounds.
Correct Answer: B — The region between 400-1500 cm-1
Q. What does the term 'Beer-Lambert Law' describe?
A.The relationship between temperature and absorbance
B.The relationship between concentration and absorbance
C.The relationship between wavelength and absorbance
D.The relationship between time and absorbance
Solution
The Beer-Lambert Law describes the linear relationship between the concentration of a solute in a solution and the absorbance of light at a specific wavelength.
Correct Answer: B — The relationship between concentration and absorbance
Q. What is the main advantage of using a diode array detector in UV-Vis spectroscopy?
A.Higher resolution
B.Simultaneous detection of multiple wavelengths
C.Lower cost
D.Simpler sample preparation
Solution
A diode array detector allows for the simultaneous detection of multiple wavelengths, enabling rapid data collection and analysis in UV-Vis spectroscopy.
Correct Answer: B — Simultaneous detection of multiple wavelengths
Q. What is the primary purpose of UV-Vis spectroscopy?
A.To measure the mass of a sample
B.To determine the concentration of a substance
C.To separate components of a mixture
D.To identify the molecular structure
Solution
UV-Vis spectroscopy is primarily used to determine the concentration of a substance in a solution based on the absorbance of light at specific wavelengths.
Correct Answer: B — To determine the concentration of a substance
Q. Which of the following compounds would you expect to show strong absorption in the UV region?
A.Alkanes
B.Aromatic compounds
C.Alcohols
D.Carboxylic acids
Solution
Aromatic compounds have delocalized π electrons that can absorb UV light, leading to strong absorption in the UV region, unlike alkanes which do not absorb UV light.
Correct Answer: B — Aromatic compounds
Q. Which of the following is NOT a common use of IR spectroscopy?
A.Identifying functional groups
B.Determining molecular weight
C.Analyzing chemical bonds
D.Studying molecular vibrations
Solution
Determining molecular weight is not a common use of IR spectroscopy; it is primarily used for identifying functional groups and analyzing molecular vibrations.
