Nuclear Magnetic Resonance Spectrometer Flashcards
1
Q
- NMR spectroscopy is used for determining structure in which of the following materials?
a) Radioactive materials
b) Insoluble chemical compounds
c) Liquids
d) Gases
A
c) Liquids
2
Q
- NMR is the study of the absorption of __________ by
nuclei in a magnetic field.
a) Radioactive radiation
b) IR radiation
c) Radio frequency radiation
d) Microwaves
A
c) Radio frequency radiation
3
Q
- NMR spectroscopy indicates the chemical nature of the __________ and spatial positions of _______
a) Electrons, Protons
b) Neutrons, electrons
c) Nuclei, electrons
d) Nuclei, neighbouring nuclei
A
d) Nuclei, neighbouring nuclei
4
Q
- NMR spectrometer provides ____________ and
_____________ method of determining structure in
soluble chemical compounds.
a) Accurate, destructive
b) Accurate, non-destructive
c) Inaccurate, destructive
d) Inaccurate, non-destructive
A
b) Accurate, non-destructive
5
Q
- In NMR spectroscopy, the spinning nuclei in a strong
magnetic field must be irradiated by which of the
following?
a) Perpendicular and stronger field
b) Perpendicular and weaker field
c) Parallel and stronger field
d) Parallel and weaker field
A
b) Perpendicular and weaker field
6
Q
- Interaction between matter and electromagnetic
radiation can be observed by subjecting a substance to
magnetic fields in which of the following manner?
a) Both fields should be stationary
b) Both fields should be varying
c) One field should be stationary and the other should be varying
d) It must be subjected to only one field
A
c) One field should be stationary and the other should be varying
7
Q
- When energy is absorbed by the sample, the absorption can be observed as a change in signal developed by which of the following components?
a) Amplifier
b) Photodetector
c) GM counter
d) Radiofrequency detector
A
d) Radiofrequency detector
8
Q
- Which of the following are considered to be the lowest form of Electromagnetic radiation?
a) IR radiation
b) Micro waves
c) UV radiation
d) Radio waves
A
d) Radio waves
9
Q
- The amount of energy available in radio frequency
radiation is sufficient for which of the following?
a) Excite an atom
b) Vibrate an atom
c) Vibrate a molecule
d) Affect the nuclear spin of an atom
A
d) Affect the nuclear spin of an atom
10
Q
- Nuclei having either the number of protons or
neutrons as odd have _______ spin.
a) Integral spin
b) Half integral spin
c) Zero spin
d) Positive spin
A
b) Half integral spin
11
Q
- If the number of protons or neutrons is even the spin of the nucleus will be which of the following?
a) Integral spin
b) Half integral spin
c) Zero spin
d) Positive spin
A
c) Zero spin
12
Q
- The difference between the field necessary for
resonance in the sample and in some arbitrary a chosen compound is which of the following?
a) Field shift
b) Matrix effects
c) Chemical shift
d) Resonance shift
A
c) Chemical shift
13
Q
- Chemical shift allows a chemist to obtain the idea of how atoms are joined together.
a) True
b) False
A
a) True
14
Q
- Elementary particles such as electrons and nucleus
have the property of spin.
a) True
b) False
A
a) True
14
Q
- Which of the following is not a type of NMR
spectrometer?
a) Minimal type
b) Maximal type
c) Multipurpose type
d) Wideline type
A
b) Maximal type
15
Q
- Which of the following NMR spectrometers have
stressed reliability and ease of operation?
a) Minimal type
b) Maximal type
c) Multipurpose type
d) Wideline type
A
a) Minimal type
16
Q
- Which of the following type of NMR spectrometer uses a frequency synthesizer to generate RF fields?
a) Minimal type
b) Maximal type
c) Multipurpose type
d) Wideline type
A
c) Multipurpose type
16
Q
- Permanent magnet cannot be used in wideline type
NMR spectrometer.
a) True
b) False
A
b) False
17
Q
- In wideline NMR spectrometers, which of the following has to be supplied to the electromagnet?
a) Slowly varying low voltage
b) Rapidly varying low voltage
c) Slowly varying scan voltage
d) Rapidly varying scan voltage
A
c) Slowly varying scan voltage
18
Q
- Which among the following NMR spectrometer is the more diverse spectrometer?
a) Minimal type
b) Maximal type
c) Multipurpose type
d) Wideline type
A
c) Multipurpose type
19
Q
- Which of the following NMR spectrometer emphasises on high performance versatility with cost being a secondary consideration?
a) Minimal type
b) Maximal type
c) Multipurpose type
d) Wideline type
A
c) Multipurpose type
20
Q
- Which of the following NMR spectrometer does not
require a power supply and cooling system?
a) Minimal type
b) Maximal type
c) Multipurpose type
d) Wideline type
A
a) Minimal type
21
Q
- Minimal type of NMR spectrometer is inexpensive.
a) True
b) False
A
a) True
22
Q
- Which of the following components are used to
separate the nuclear spin energy states?
a) RF channels
b) Magnet
c) Sample probe
d) Sweep generator
A
b) Magnet
23
10. Which of the following is used as a coolant for magnets in continuous-wave NMR spectrometer?
a) Water
b) Liquid He
c) Liquid Na
d) Heavy water
a) Water
24
4. Which of the following statements are not true about permanent magnets?
a) They are simple
b) They are inexpensive
c) They don’t require shielding
d) They don’t require power supply
c) They don’t require shielding
24
2. In frequency sweep method, which of the following
parameters are varied continuously?
a) Magnetic field
b) RF signal
c) Sample concentration
d) Amplification factor
b) RF signal
25
3. In field sweep method, which of the following
parameters are varied continuously?
a) Magnetic field
b) RF signal
c) Sample concentration
d) Amplification factor
a) Magnetic field
26
9. The single coil probe supplies the RF radiation to the
sample and also serves as a part of which of the following
circuits?
a) RF channels
b) Magnet
c) Detector
d) Sweep generator
c) Detector
26
5. Which of the following is not true of electromagnets?
a) They are expensive
b) They require a power supply
c) They don’t require a cooling system
d) They don’t require extensive shielding
c) They don’t require a cooling system
26
12. The voltage generated by the receiver coil is small and it must be amplified.
a) True
b) False
a) True
27
7. Which of the following must not be done to maintain the magnetic field over the sample uniform in space and time?
a) Large pole pieces need to be used
b) Pole faces must be polished
c) Wide pole gap must be present
d) Magnets can be permanent or electromagnet
c) Wide pole gap must be present
27
6. For high resolution work the magnetic field over the
entire sample volume must be maintained uniform in
space and time.
a) True
b) False
a) True
28
10. Nuclear induction probes’ one coil is used for signal detection. What is the function of the other coil?
a) Sample irradiation
b) Magnet
c) Detector
d) Sweep generator
a) Sample irradiation
28
8. The sample is contained in which of the following
components?
a) Flask
b) Capillary tube
c) Curvette
d) Bore glass tube
d) Bore glass tube
29
13. The amplification required for continuous-wave NMR is of the order of which of the following?
a) 10&1
b) 10^2
c) 10^3
d) 10^5
d) 10^5
30
14. Which of the following can be used instead of magnets to produce the magnetic field?
a) Inductor
b) Motor
c) Generator
d) Superconducting solenoids
d) Superconducting solenoids
31
15. How is the inhomogeneity of magnetic fields
compensated?
a) With large magnetic fields
b) With small magnetic fields
c) By using two or more magnets
d) By providing required insulation
View Answer
b) With small magnetic fields
32
2. Fourier transform NMR spectrometer has which of the following characteristics?
a) Increased sensitivity, long time to obtain data
b) Decreased sensitivity, long time to obtain data
c) Increased sensitivity, reduced time to obtain data
d) Decreased sensitivity, reduced time to obtain data
c) Increased sensitivity, reduced time to obtain data
32
1. Fourier transform NMR spectrometer allows NMR
transitions to be observed simultaneously.
a) True
b) False
a) True
33
3. Which of the following cannot be done due to the
multiplex advantage?
a) Repetitive signals can be summed
b) Repetitive signals can be averaged
c) Increases signal to noise ratio
d) Decreases signal to noise ratio
d) Decreases signal to noise ratio
34
4. Two coils are necessary for Fourier transform NMR
spectroscopy.
a) True
b) False
b) False
35
5. Which of the following is the disadvantage of
conventional mode of spectrometer or continuous-wave NMR spectrometer?
a) They are unstable
b) Maintenance is difficult
c) High operating cost
d) Excitation is inefficient
d) Excitation is inefficient
36
6. Which of the following must be done to improve
sensitivity?
a) Frequency sweep mode must be preferred
b) Field sweep mode must be preferred
c) Single channel excitation must be preferred
d) Multichannel excitation must be preferred
d) Multichannel excitation must be preferred
37
7. Which of the following is the disadvantage of
multichannel excitation?
a) Low sensitivity
b) Low resolution
c) Small number of frequencies is present
d) Uneconomical
d) Uneconomical
38
8. How can the need for an array of narrow-band filters and detectors be eliminated?
a) By using multi-channel excitation
b) By using a detector for each frequency
c) By reducing the number of detectors
d) By using Fourier transform
d) By using Fourier transform
39
9. Fourier transform can be accomplished by using which of the following components?
a) Spin decoder
b) Detector
c) Spectrum analyser
d) Oscilloscope
c) Spectrum analyser
40
10. A 15.4 MHz crystal generates the _________
resonance frequency.
a) Hydrogen
b) Deuterium
c) Tritium
d) Helium
b) Deuterium
41
1. Sensitivity is the ratio of peak signal amplitude to which of the following?
a) Time
b) Rms noise
c) Average noise
d) Peak-to-peak noise
b) Rms noise
42
2. Which of the following is not an operating technique for sensitivity enhancement?
a) Optimization of sample volume
b) Optimization of instrumental parameters
c) Optimization of noise
d) Time averaging
c) Optimization of noise
43
3. Which of the following techniques do not enhance
sensitivity by a factor of 10 at normal operating
conditions?
a) Optimization of sample volume
b) Optimization of instrumental parameters
c) Optimization of noise
d) Time averaging
d) Time averaging
44
4. The most common spherical cells have which of the
following dimensions?
a) 4mm diameter
b) 40mm diameter
c) 8mm diameter
d) 80mm diameter
a) 4mm diameter
45
5. Better sensitivity with good resolution can be achieved by concentrating the sample inside which of the following?
a) Sample cell
b) Micro cell
c) Sample tube
d) Cylindrical tube
b) Micro cell
46
6. Frequency spectrum of noise occupies a band that is
_________ the signal spectrum. Choose the most
appropriate option.
a) Narrow than
b) Wider than
c) Different from
d) Same as
b) Wider than
47
7. Suppression of frequencies which contain no signal does which of the following?
a) Increases S/N ratio
b) Decreases S/N ratio
c) S/N ratio is kept constant
d) S/N ratio becomes 1
a) Increases S/N ratio
48
8. The amplitude of the NMR signal caused by the
absorption of RF energy at the radio frequency does not depend upon the power of the RF energy applied.
a) True
b) False
b) False
49
9. Which of the following is not involved in signal
averaging?
a) A system to repeatedly scan the spectral region of
interest
b) Some storage device to store information
c) A system to coherently add individual spectra
d) Sweep generator
d) Sweep generator
50
10. In order to have a long measuring time for increasing sensitivity, it is better to have several fast scans than a single slow scan.
a) True
b) False
a) True
