SPECTROSCOPY
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Time limit: 20 minutes
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Question 1
Multiple choiceWhy is the Beer-Lambert law important in quantitative analysis?
Explanation
Beer-Lambert law is crucial because it allows for the calculation of concentration based on measured absorbance.
Question 2
Multiple choiceWhat is the primary focus of spectroscopy?
Explanation
Spectroscopy is defined as the study of the interaction between matter and electromagnetic radiation.
Question 3
Multiple choiceWhich of the following describes a spectrum?
Explanation
A spectrum is a plot that represents the response of interest (such as absorbance) as a function of wavelength or frequency.
Question 4
Multiple choiceWhat device is used for making relative measurements in optical spectroscopy?
Explanation
A spectrometer is an instrument specifically used for making measurements in the optical spectral region.
Question 5
Multiple choiceWhich of the following light sources is commonly used in UV-VIS spectrophotometry for the visible region?
Explanation
The tungsten halogen lamp is the most common light source used in visible spectrophotometry.
Question 6
Multiple choiceWhat type of energy transition does absorption spectroscopy primarily focus on?
Explanation
Absorption spectroscopy focuses primarily on electronic transitions where electrons are promoted from a lower energy state to a higher energy state.
Question 7
Multiple choiceWhat is the wavelength range for the visible spectrum?
Explanation
The visible region of the spectrum extends approximately over the wavelength range of 400-700 nm.
Question 8
Multiple choiceWhich principle describes the absorbance at a certain wavelength being proportional to the concentration of an absorbing species?
Explanation
The Beer-Lambert Law states that the absorbance is directly proportional to the concentration of the absorbing species.
Question 9
Multiple choiceWhich of the following describes a photomultiplier tube?
Explanation
A photomultiplier tube is a detector commonly used in UV-Vis spectroscopy that converts light into an electrical signal.
Question 10
Multiple choiceWhich wavelength transition is typically observed in carbonyl compounds?
Explanation
Carbonyl compounds often show n → π* transitions around 300 nm due to their structure.
Question 11
Multiple choiceWhat effect does increased solvent polarity have on n → π* transitions?
Explanation
Increasing solvent polarity causes a blue shift in n → π* transitions due to solvent interactions with the ground state.
Question 12
Multiple choiceWhich type of spectroscopy measures the light scattered by a substance?
Explanation
Scattering spectroscopy focuses on measuring light that is scattered by a substance rather than absorbed.
Question 13
Multiple choiceWhat is the primary purpose of auxochromes in spectroscopy?
Explanation
Auxochromes enhance the intensity and often the wavelength of absorption when attached to a chromophore.
Question 14
Multiple choiceWhat does the term 'bathochromic shift' refer to?
Explanation
A bathochromic shift refers to the shift of absorption to longer wavelengths, indicating lower energy transitions.
Question 15
Multiple choiceWhich type of spectroscopy is especially important in the analysis of multi-component systems?
Explanation
UV-Vis spectroscopy is crucial for analyzing multi-component systems based on absorbance at specific wavelengths.
Question 16
Multiple choiceWhich of the following describes a single beam spectrophotometer?
Explanation
A single beam spectrophotometer measures absorbance intensity of the sample and reference serially, providing higher sensitivity due to its simpler design.
Question 17
Multiple choiceWhat does the extinction coefficient (ε) indicate in spectroscopy?
Explanation
The extinction coefficient (ε) represents the molar absorptivity of a substance under specific conditions in UV-Vis spectroscopy.
Question 18
Multiple choiceIn UV-Vis spectroscopy, which components are essential for measuring absorbance?
Explanation
A cuvette (sample holder) and detector are essential for measuring absorbance in UV-Vis spectroscopy.
Question 19
Multiple choiceWhat type of spectroscopy measures the amount of light that a substance scatters at certain wavelengths?
Explanation
Raman spectroscopy is a type of scattering spectroscopy that focuses on measuring the scattered light from a substance to gain information about its physical properties.
Question 20
Multiple choiceWhich of the following statements correctly describes the Beer-Lambert law?
Explanation
The Beer-Lambert law states that the amount of light absorbed by a substance is directly proportional to both the concentration of the substance and the path length through which the light passes.