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Chemical Technician (Analytical Chemistry) > Nuclear Magnetic Resonance Spectrometer > Flashcards

Nuclear Magnetic Resonance Spectrometer Flashcards

1
Q
  1. 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

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2
Q
  1. 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

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3
Q
  1. 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

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4
Q
  1. 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

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5
Q
  1. 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

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6
Q
  1. 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

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7
Q
  1. 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

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8
Q
  1. 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

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9
Q
  1. 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

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10
Q
  1. 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

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11
Q
  1. 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

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12
Q
  1. 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

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13
Q
  1. Chemical shift allows a chemist to obtain the idea of how atoms are joined together.
    a) True
    b) False
A

a) True

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14
Q
  1. Elementary particles such as electrons and nucleus
    have the property of spin.
    a) True
    b) False
A

a) True

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14
Q
  1. 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

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15
Q
  1. 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

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16
Q
  1. 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

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16
Q
  1. Permanent magnet cannot be used in wideline type
    NMR spectrometer.
    a) True
    b) False
A

b) False

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17
Q
  1. 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

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18
Q
  1. 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

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19
Q
  1. 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

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20
Q
  1. 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

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21
Q
  1. Minimal type of NMR spectrometer is inexpensive.
    a) True
    b) False
A

a) True

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22
Q
  1. 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
23
Q
  1. 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
24
Q
  1. 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
A

c) They don’t require shielding

24
Q
  1. In frequency sweep method, which of the following
    parameters are varied continuously?
    a) Magnetic field
    b) RF signal
    c) Sample concentration
    d) Amplification factor
A

b) RF signal

25
Q
  1. 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

a) Magnetic field

26
Q
  1. 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
A

c) Detector

26
Q
  1. 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
A

c) They don’t require a cooling system

26
Q
  1. The voltage generated by the receiver coil is small and it must be amplified.
    a) True
    b) False
27
Q
  1. 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
A

c) Wide pole gap must be present

27
Q
  1. For high resolution work the magnetic field over the
    entire sample volume must be maintained uniform in
    space and time.
    a) True
    b) False
28
Q
  1. 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

a) Sample irradiation

28
Q
  1. The sample is contained in which of the following
    components?
    a) Flask
    b) Capillary tube
    c) Curvette
    d) Bore glass tube
A

d) Bore glass tube

29
Q
  1. 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
30
Q
  1. Which of the following can be used instead of magnets to produce the magnetic field?
    a) Inductor
    b) Motor
    c) Generator
    d) Superconducting solenoids
A

d) Superconducting solenoids

31
Q
  1. 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
A

b) With small magnetic fields

32
Q
  1. 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
A

c) Increased sensitivity, reduced time to obtain data

32
Q
  1. Fourier transform NMR spectrometer allows NMR
    transitions to be observed simultaneously.
    a) True
    b) False
33
Q
  1. 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
A

d) Decreases signal to noise ratio

34
Q
  1. Two coils are necessary for Fourier transform NMR
    spectroscopy.
    a) True
    b) False
35
Q
  1. 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
A

d) Excitation is inefficient

36
Q
  1. 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
A

d) Multichannel excitation must be preferred

37
Q
  1. 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
A

d) Uneconomical

38
Q
  1. 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
A

d) By using Fourier transform

39
Q
  1. Fourier transform can be accomplished by using which of the following components?
    a) Spin decoder
    b) Detector
    c) Spectrum analyser
    d) Oscilloscope
A

c) Spectrum analyser

40
Q
  1. A 15.4 MHz crystal generates the _________
    resonance frequency.
    a) Hydrogen
    b) Deuterium
    c) Tritium
    d) Helium
A

b) Deuterium

41
Q
  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
A

b) Rms noise

42
Q
  1. 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
A

c) Optimization of noise

43
Q
  1. 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
A

d) Time averaging

44
Q
  1. The most common spherical cells have which of the
    following dimensions?
    a) 4mm diameter
    b) 40mm diameter
    c) 8mm diameter
    d) 80mm diameter
A

a) 4mm diameter

45
Q
  1. 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
A

b) Micro cell

46
Q
  1. 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
A

b) Wider than

47
Q
  1. 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

a) Increases S/N ratio

48
Q
  1. 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
49
Q
  1. 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
A

d) Sweep generator

50
Q
  1. 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

Chemical Technician (Analytical Chemistry) (16 decks)

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