IR Spectroscopy MCQs: 53

 IR Spectroscopy MCQs

1. Range of far IR 

1. 400-33 cm−1 

2. 4000-400 cm−1

3. 12820- 4000 cm−1

4. 10-400 cm−1

2. Interferometer is present in 

1. FTIR

2. AAS

3. AES

4. NMR

3. Which of the following has longest wavelength? 

1. Far IR

2. Mid IR

3. Near IR 

4. All

4.  Select the correct one 

1. Stretching vibration means change in bong length between two atoms

2. Stretching vibration need more energy 

3. Bending Vibration require less energy 

4. All 

5. Non-dispersive IR will not have a 

1. Radiation source

2. Detector 

3. Monochromator 

4. none

6. IR region most commonly used for qualitative analysis is 

1. Far

2. Near 

3. Mid 

4. None

7. Which of the following is not a source of Mid-IR region ‘

1. Nernst glower 

2. Globar source

3. Nichrome wire 

4. High pressure mercury arc 

8. Solid samples in IR, correct one 

1. Solids are examined as thin paste or mull

2. Mull is prepared by grinding 2-5 milligrams of the sample in presence of one or two hydrocarbon oil 

3. Small quantity of sample + 100-300mg of potassium bromide  

4. All 

9. The solvent not used in IR spectroscopy is 

1. Chloroform 

2. Carbon tetra chloride

3. Carbon disulphide 

4. Water 

10. Bolometer a type of detector also called as

1. Thermistor 

2. Thermocouple

3. Golay

4. Resistance temperature detector

11. Which prism will you use for IR spectroscopy 

1. Glass prism

2. Fused silica prism 

3. Prism coated with sodium chloride

4. All

12. As wave number increases what happens to wave energy

1. Increase

2. Decreases

3. No relation 

4. Remains constant 

13. Which of the following is not a thermal detector used in IR 

1. Photoconductivity 

2. Thermocouple

3. Bolometer

4. Golay 

14. Which of the following is in- plane bending vibration

1. Scissoring 

2. Wagging

3. Twisting 

4. None 

15. In IR spectroscopy samples can be prepared by 

1. Sodium chloride 

2. Nujol oil

3. KBr 

4. All

16. IR spectroscopy is usually used to determine 

1. Functional group

2. No. of Proton 

3. Molecular structure 

4. All 

17.  2250 per cm is base value for the absorption of bonds 

1. O-H 

2. N-H 

3. C-H 

4. C ≡N 

18. For calibration of wave number what is used

1. Polystyrene film

2. Potassium dichromate

3. Holonium filter 

4. Polyvinyl film 

19. For obtaining IR Nernst filament is heated on 

1. 500-1000

2. 1000-1500

3. 2000-2500

4. 1000-1800

1. None 

20. Which compound can have same pattern of absorption in finger print region 

1. Isomers

2. Diasteremors

3. Enantiomers 

4. Isoteres

21. Which of the following detectors are based on expansion of gas 

1. Golay

2. Bolometers

3. Pyroelectric

4. Photoconductivity cell

22. Distance between two atom increases or decreases although the atoms remain in same axis. The statement is true for following type of axis 

1. Stretching 

2. Rocking

3. Twisting

4. Wagging

23. For the given bond, which type of vibration will occur at highest frequency from the following 

1. In-plane bending 

2. Out of plane bending 

3. Symmetric stretching 

4. Asymmetric stretching 

24. What is the wavenumber for the IR radiation having wavelength 25 micrometer?

1. 4000

2. 400

3. 2500

4. 250 

25. H bonded O-H structure of alcohol occurs at following wave number in IR spectrum 

1. 3400-3650

2. 17250-1100

3. 3400-2400

4. 1640-1550

26.  Globar sources of IR radiation 

1. Rod of silicon carbide

2. Heated up to 1300°C

3. Produce radiant energy from 1-40 micron

4. All of the above 

27. In IR, absorption causes 

1. Changes in electron spin 

2. Changes in rotational and vibrational energy states

3. Ejection of inner electron

4. Changes in nucleus 

28. Electrons do not absorb EMR in following spectroscopy 

1. UV

2. NMR

3. AAS

4. IR

29. Quick identification of a compound is possible with help of 

1. Mass spectra

2. NMR spectra

3. IR spectra

4. UV spectra 

30. The OH absorption band in IR spectra appears 

1. Below 1000 cm−1

2. Below 1800 cm−1

3. Above 3500 cm−1

4. Just below 3000 cm−1

31. Fingerprint region 

1. 4000-600 cm−1

2. 4000-1500 cm−1

3. 1500-600 cm−1

4. 12500-4000 cm−1

32. Which of the following compound is IR active? 

1. Hydrogen 

2. N2

3. Trans-1,2 dichloromethene 

4. Cis-1, 2 dichloromethene 

33. When a fundamental vibration couples with overtone or combination band, the coupled vibration is called as 

1. Differential band

2. Combination

3. Dipole moment 

4. Fermi resonance 

34. Absorption band corresponding µ=0 to µ=1 is called 

1. Fundamental absorption band

2. Overtone

3. Fermi resonance

4. Combination band 

35. If fundamental band occurs at 800 cm−1 then second overtone will occur at 

1. 800 cm−1

2. 1600 cm−1

3. 3200 cm−1

4. 2400 cm−1

36. Which compound is used as diluent in IR 

1. Alkali halide

2. Aldehyde

3. NaOH

4. Acetone 

What is the range of far-infrared (Far IR)?

The range of Far IR is 10-400 cm⁻¹.

In which instrument is an interferometer present?

An interferometer is present in Fourier Transform Infrared (FTIR) Spectroscopy.

Which region of IR has the longest wavelength?

Far IR has the longest wavelength compared to Mid-IR and Near-IR.

Which statement about stretching and bending vibrations is correct?

- Stretching vibration means a change in bond length between two atoms.
- Stretching vibrations require more energy than bending vibrations.
- Bending vibrations require less energy.
- All of the above are correct.

What does a non-dispersive IR spectrometer lack?

A non-dispersive IR spectrometer lacks a monochromator.

Which IR region is most commonly used for qualitative analysis?

Mid-IR (4000-400 cm⁻¹) is most commonly used for qualitative analysis.

Which is NOT a source of Mid-IR radiation?

Nichrome wire is NOT a source of Mid-IR radiation.
Common sources include Nernst glower, Globar source, and high-pressure mercury arc.

How are solid samples prepared for IR analysis?

Solid samples in IR spectroscopy can be prepared using:
- Thin paste or mull method (grinding the sample with hydrocarbon oil).
- Potassium bromide (KBr) pellet method (mixing the sample with KBr and compressing it).

Which solvent is NOT used in IR spectroscopy?

Water is NOT used in IR spectroscopy because it absorbs strongly in the IR region.

What is another name for a bolometer detector?

A bolometer is also called a thermistor.

Which prism is used in IR spectroscopy?

Prisms coated with sodium chloride (NaCl) are used in IR spectroscopy.

What happens to energy as the wavenumber increases?

As the wavenumber increases, energy also increases.

Which is NOT a thermal detector in IR spectroscopy?

Photoconductivity detectors are NOT thermal detectors.

Which vibration is an in-plane bending vibration?

Scissoring is an in-plane bending vibration.

What are the methods for preparing samples in IR spectroscopy?

Samples can be prepared using:
- Sodium chloride plates
- Nujol oil mull
- Potassium bromide (KBr) pellets

What is IR spectroscopy used for?

IR spectroscopy is used to determine functional groups in a molecule.

What is the base wavenumber for the absorption of a C≡N bond?

The C≡N (nitrile) bond absorbs around 2250 cm⁻¹.

What is used for calibration of wavenumbers in IR?

Polystyrene film is used for calibration.

What is the temperature range for heating the Nernst filament in IR?

The Nernst filament is heated to 1000-1500°C.

Which compounds can have the same absorption pattern in the fingerprint region?

Enantiomers can have the same absorption pattern in the fingerprint region.

Which IR detector is based on gas expansion?

The Golay detector works on the expansion of gas.

Which vibration occurs at the highest frequency?

Asymmetric stretching occurs at the highest frequency.

What is the fingerprint region in IR spectroscopy?

The fingerprint region is 1500-600 cm⁻¹.

Which compound is IR-active?

Cis-1,2-dichloromethene is IR-active because it has a permanent dipole moment.

What is Fermi resonance?

When a fundamental vibration couples with an overtone or combination band, it is called Fermi resonance.

What compound is used as a diluent in IR spectroscopy?

Alkali halides (e.g., potassium bromide, KBr) are commonly used as diluents.