Qualitative Analysis: Master Functional Group Identification and Spectroscopy Techniques

Question 1

Which spectroscopic technique is predominantly used for identifying functional groups due to its ability to detect different bond vibrations?

Accepted Answer

Infrared (IR) Spectroscopy

Answer

Nuclear Magnetic Resonance (NMR)

Answer

Ultraviolet-Visible (UV-Vis) Spectroscopy

Answer

Mass Spectrometry

Question 2

Within the IR spectrum, what frequency range (in cm^-1) is characteristic of the carbonyl group (C=O) absorption?

Accepted Answer

1500-1800

Answer

650-850

Answer

2500-3000

Answer

3200-3600

Question 3

In NMR spectroscopy, what is the primary function of a chemical shift reagent?

Accepted Answer

To modify the magnetic field experienced by atomic nuclei

Answer

To increase the relaxation time of atomic nuclei

Answer

To improve the signal-to-noise ratio

Answer

To suppress unwanted peaks

Question 4

The Dragendorff's test is commonly used for the detection of which class of compounds?

Accepted Answer

Alkaloids

Answer

Phenols

Answer

Carbohydrates

Answer

Amines

Question 5

The presence of a strong, broad peak in the IR spectrum at around 3300 cm^-1 can indicate the presence of which functional group?

Accepted Answer

Alcohol

Answer

Aldehyde

Answer

Ketone

Answer

Carboxylic acid

Question 6

Which of the following compounds will exhibit a strong absorption peak in the UV spectrum at a wavelength of approximately 280 nm?

Accepted Answer

Benzene

Answer

Ethanol

Answer

Acetic acid

Answer

Sodium chloride

Question 7

Which of the following ions is not detected using the flame test?

Accepted Answer

Iron

Answer

Sodium

Answer

Potassium

Answer

Calcium

Question 8

The qualitative analysis of a drug sample indicates the presence of a primary amine functional group. Which of the following reagents can be used to confirm this finding?

Accepted Answer

Ninhydrin

Answer

2,4-dinitrophenylhydrazine

Answer

Benedict's reagent

Answer

Tollens' reagent

Question 9

Which spectroscopic technique is most commonly used for identifying the presence of a carbonyl group?

Accepted Answer

Infrared (IR) spectroscopy

Answer

Ultraviolet (UV) spectroscopy

Answer

Nuclear magnetic resonance (NMR) spectroscopy

Answer

Mass spectrometry

Question 10

What is the fundamental principle behind mass spectrometry?

Accepted Answer

Separation of ions based on their mass-to-charge ratio

Answer

Detection of atoms and molecules based on their absorption of electromagnetic radiation

Answer

Measurement of the nuclear spin of atoms

Answer

Identification of functional groups based on their characteristic vibrational frequencies

Question 11

Which type of NMR spectroscopy is primarily used to determine the connectivity of atoms within a molecule?

Accepted Answer

2D NMR

Answer

1H NMR

Answer

13C NMR

Answer

DEPT NMR

Question 12

In IR spectroscopy, which type of vibration results in a strong and broad absorption band between 3200 and 3600 cm-1?

Accepted Answer

O-H stretching

Answer

C-H stretching

Answer

C=O stretching

Answer

N-H stretching

Question 13

Which of the following techniques is used to determine the molecular weight of organic compounds?

Accepted Answer

Mass spectrometry

Answer

NMR spectroscopy

Answer

UV spectroscopy

Answer

HPLC

Question 14

Which of the following is a limitation of qualitative analysis compared to quantitative analysis?

Accepted Answer

Qualitative analysis cannot provide precise measurements of analyte concentration

Answer

Qualitative analysis is more time-consuming and requires specialized equipment

Answer

Qualitative analysis is less versatile and cannot be used for a wide range of compounds

Answer

Qualitative analysis is not suitable for regulatory purposes

Question 15

When selecting a solvent for extraction in qualitative analysis, which factor should be considered?

Accepted Answer

The solvent's polarity relative to the analyte

Answer

The solvent's boiling point

Answer

The solvent's toxicity

Answer

The solvent's availability

Question 16

After obtaining a positive result for the presence of a particular functional group in a qualitative analysis experiment, what should be the next step?

Accepted Answer

Confirm the result using a different analytical technique

Answer

Quantify the amount of the functional group present

Answer

Identify the specific compound containing the functional group

Answer

Report the result without further investigation

Question 17

Which functional group exhibits a strong, broad absorption band around 3300 cm⁻¹ in the infrared (IR) spectrum?

Accepted Answer

Hydroxyl group (O-H)

Answer

Alkyl group (C-H)

Answer

Carbonyl group (C=O)

Answer

Alkene group (C=C)

Question 18

Which spectroscopic technique is most effective for determining both the molecular weight and structural information of an unknown organic compound?

Accepted Answer

Mass Spectrometry

Answer

UV-Vis Spectroscopy

Answer

Infrared (IR) Spectroscopy

Answer

Nuclear Magnetic Resonance (NMR) Spectroscopy

Question 19

Which statement is NOT true about UV-Vis Spectroscopy?

Accepted Answer

It can determine the exact molecular weight of a compound.

Answer

It provides insights into the conjugation within a molecule.

Answer

It is used to analyze the purity of a compound.

Answer

It relies on the absorption of ultraviolet-visible light by molecules.

Question 20

A positive result in the 2,4-Dinitrophenylhydrazine (2,4-DNP) test indicates the presence of which functional group?

Accepted Answer

Carbonyl group (aldehyde or ketone)

Answer

Carboxylic acid

Answer

Amine

Answer

Alcohol

Question 21

Which qualitative analytical technique separates and identifies components of a mixture based on their differing affinities for a stationary and mobile phase?

Accepted Answer

Chromatography

Answer

Spectrophotometry

Answer

Gravimetric analysis

Answer

Titration

Question 22

In mass spectrometry, what does the base peak in a mass spectrum represent?

Accepted Answer

The most abundant ion.

Answer

The ion with the lowest relative abundance.

Answer

The fragment ion with the highest mass-to-charge ratio.

Answer

The molecular ion.

Question 23

What is the primary purpose of using a derivatization reagent in qualitative analysis?

Accepted Answer

To enhance the detectability or volatility of the analyte.

Answer

To increase the solubility of the analyte in water.

Answer

To neutralize the pH of the sample.

Answer

To convert the analyte into a more stable form.

Question 24

Which of the following is NOT a typical application of qualitative analysis in the pharmaceutical industry?

Accepted Answer

Determining the shelf life of a drug product.

Answer

Monitoring the progress of a reaction during drug synthesis.

Answer

Confirming the presence of functional groups in a synthesized drug molecule.

Answer

Identifying unknown impurities in a drug substance.