Intro to Spectroscopy (UV-Vis, IR) - Competitive Exam Level
Q. In IR spectroscopy, which bond typically shows a strong absorption around 3300 cm-1?
A.C-H bond
B.N-H bond
C.O-H bond
D.C=O bond
Solution
The O-H bond in alcohols and carboxylic acids typically shows a strong absorption around 3300 cm-1 due to the stretching vibration.
Correct Answer: C — O-H bond
Q. In IR spectroscopy, which functional group typically shows a strong absorption around 1700 cm-1?
A.Alcohols
B.Aldehydes
C.Carboxylic acids
D.Ketones
Solution
Ketones typically show a strong carbonyl (C=O) absorption around 1700 cm-1 due to the stretching vibration.
Correct Answer: D — Ketones
Q. In UV-Vis spectroscopy, what does a higher absorbance indicate?
A.Lower concentration of the analyte
B.Higher concentration of the analyte
C.Higher wavelength of light
D.Lower energy of light
Solution
A higher absorbance indicates a higher concentration of the analyte, as per the Beer-Lambert Law.
Correct Answer: B — Higher concentration of the analyte
Q. What is the main advantage of using a UV-Vis spectrophotometer?
A.It can analyze solid samples
B.It provides real-time analysis
C.It requires no sample preparation
D.It can measure very low concentrations
Solution
One of the main advantages of UV-Vis spectrophotometry is that it can measure very low concentrations of analytes in solution.
Correct Answer: D — It can measure very low concentrations
Q. What type of transition is primarily observed in UV-Vis spectroscopy?
A.Nuclear spin transitions
B.Rotational transitions
C.Electronic transitions
D.Vibrational transitions
Solution
UV-Vis spectroscopy primarily observes electronic transitions, where electrons move between different energy levels.
Correct Answer: C — Electronic transitions
Q. Which of the following is NOT a common application of IR spectroscopy?
A.Identifying functional groups
B.Determining molecular weight
C.Studying molecular vibrations
D.Analyzing chemical bonds
Solution
Determining molecular weight is not a common application of IR spectroscopy; it is primarily used for identifying functional groups and studying molecular vibrations.
