Q. If a compound has a molar absorptivity of 200 L/(mol·cm) and a concentration of 0.01 mol/L, what is the absorbance at a path length of 1 cm?
A.
0.2
B.
2
C.
20
D.
0.02
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Solution
Using Beer-Lambert Law (A = εlc), A = 200 L/(mol·cm) * 0.01 mol/L * 1 cm = 2.
Correct Answer:
A
— 0.2
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Q. If a sample absorbs light at 250 nm with an absorbance of 0.5, what is the transmittance?
A.
50%
B.
25%
C.
75%
D.
100%
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Solution
Transmittance (T) can be calculated using the formula T = 10^(-A). For A = 0.5, T = 10^(-0.5) = 0.316, which is approximately 50%.
Correct Answer:
A
— 50%
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Q. If a solution has a concentration of 0.1 M and a path length of 1 cm, what is the absorbance if ε = 200 L/(mol·cm)?
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Solution
Using Beer-Lambert Law, A = εcl = 200 L/(mol·cm) * 0.1 mol/L * 1 cm = 20.
Correct Answer:
C
— 2
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Q. In a UV-Vis spectrum, what does a peak at 260 nm typically indicate?
A.
Proteins
B.
Nucleic acids
C.
Lipids
D.
Carbohydrates
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Solution
A peak at 260 nm is characteristic of nucleic acids, particularly DNA and RNA.
Correct Answer:
B
— Nucleic acids
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Q. In IR spectroscopy, which functional group is characterized by a strong absorption around 1700 cm-1?
A.
Alcohols
B.
Aldehydes
C.
Carboxylic acids
D.
Ketones
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Solution
Ketones typically show a strong carbonyl (C=O) absorption around 1700 cm-1 in IR spectroscopy.
Correct Answer:
D
— Ketones
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Q. In IR spectroscopy, which functional group is indicated by a strong peak around 1700 cm-1?
A.
Alcohol
B.
Aldehyde
C.
Carboxylic Acid
D.
Carbonyl
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Solution
A strong peak around 1700 cm-1 in IR spectroscopy is characteristic of the carbonyl (C=O) functional group.
Correct Answer:
D
— Carbonyl
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Q. In UV-Vis spectroscopy, what does a higher absorbance indicate about the concentration of a sample?
A.
Lower concentration
B.
Higher concentration
C.
No correlation
D.
Increased path length
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Solution
According to Beer-Lambert Law, higher absorbance indicates a higher concentration of the absorbing species.
Correct Answer:
B
— Higher concentration
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Q. What is the Beer-Lambert Law equation?
A.
A = εcl
B.
A = c/εl
C.
A = l/εc
D.
A = cl/ε
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Solution
The Beer-Lambert Law is expressed as A = εcl, where A is absorbance, ε is molar absorptivity, c is concentration, and l is path length.
Correct Answer:
A
— A = εcl
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Q. What is the effect of increasing the path length in a UV-Vis spectrophotometer?
A.
Decreases absorbance
B.
Increases absorbance
C.
No effect on absorbance
D.
Increases wavelength
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Solution
Increasing the path length increases the absorbance according to Beer-Lambert Law.
Correct Answer:
B
— Increases absorbance
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Q. What is the primary purpose of using a blank in UV-Vis spectroscopy?
A.
To calibrate the instrument
B.
To measure the sample absorbance
C.
To account for solvent effects
D.
To determine the concentration
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Solution
A blank is used to account for any absorbance due to the solvent or other components in the sample.
Correct Answer:
C
— To account for solvent effects
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Q. What is the primary use of IR spectroscopy in organic chemistry?
A.
Determining molecular weight
B.
Identifying functional groups
C.
Measuring concentration
D.
Analyzing reaction rates
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Solution
IR spectroscopy is primarily used to identify functional groups in organic compounds based on their characteristic absorption bands.
Correct Answer:
B
— Identifying functional groups
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Q. What is the typical range of wavelengths for infrared (IR) spectroscopy?
A.
400-700 nm
B.
700-1400 nm
C.
1400-4000 nm
D.
4000-10000 nm
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Solution
Infrared spectroscopy typically operates in the range of 1400 to 4000 nm.
Correct Answer:
C
— 1400-4000 nm
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Q. What is the wavelength range of UV-Vis spectroscopy?
A.
100-400 nm
B.
400-700 nm
C.
700-1000 nm
D.
1000-2000 nm
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Solution
UV-Vis spectroscopy typically covers the wavelength range from 100 to 400 nm for UV and 400 to 700 nm for visible light.
Correct Answer:
A
— 100-400 nm
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Q. Which of the following is NOT a common application of UV-Vis spectroscopy?
A.
Determining protein concentration
B.
Measuring pH
C.
Analyzing colored compounds
D.
Monitoring reaction kinetics
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Solution
UV-Vis spectroscopy is not typically used for direct pH measurement.
Correct Answer:
B
— Measuring pH
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Q. Which type of spectroscopy is best suited for identifying functional groups in organic compounds?
A.
NMR
B.
UV-Vis
C.
IR
D.
Mass Spectrometry
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Solution
Infrared (IR) spectroscopy is best suited for identifying functional groups due to its ability to measure molecular vibrations.
Correct Answer:
C
— IR
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Showing 1 to 15 of 15 (1 Pages)
The Intro to Spectroscopy (UV–Vis, IR) – Numerical Applications section is dedicated to quantitative problem solving involving spectroscopic principles. This module is designed for Class 11–12 students, undergraduate learners, and competitive exam aspirants , with strong emphasis on accuracy, formula application, and data interpretation .
In this section, you will practice:
Numericals on electromagnetic radiation – wavelength, frequency, energy, and photon calculations
Beer–Lambert law calculations – absorbance, concentration, molar absorptivity, and path length
UV–Vis quantitative analysis problems – concentration determination and calibration curves
Deviation-based numericals – instrumental, chemical, and real deviations from Beer’s law
IR spectroscopy calculations – wavenumber–wavelength conversions and frequency analysis
Spectral data interpretation numericals – peak position shifts and intensity comparisons
Mixed-data problems combining tables, graphs, and spectra
NCERT- and UG-aligned numerical MCQs , including previous-year and exam-pattern questions
The content is structured to build numerical confidence , minimize calculation errors , and improve speed under exam conditions .
Strengthen your quantitative command over UV–Vis and IR spectroscopy by mastering these numerical applications , essential for scoring well in school exams, UG assessments, and competitive Chemistry tests .
