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ANAL CHEM > ANAL CHEM 5 > Flashcards

ANAL CHEM 5 Flashcards

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1
Q

NMR spectroscopy is used for determining structure in which of the following materials?

Radioactive materials
Insoluble chemical compounds
Liquids
Gases

A

Liquids

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2
Q

NMR is the study of absorption of __________ by nuclei in a magnetic field?

Radioactive radiation
IR radiation
Radio frequency radiation
Microwaves

A

Radio frequency radiation

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3
Q

NMR spectrometer provides ____________ and _____________ method of determining structure
in soluble chemical compounds.

Accurate, destructive
Accurate, non-destructive
Inaccurate, destructive
Inaccurate, non-destructive

A

Accurate, non-destructive

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4
Q

NMR spectroscopy indicates the chemical nature of the __________ and spatial positions of _______

Electrons, Protons
Neutrons, electrons
Nuclei, electrons
Nuclei, neighbouring nuclei

A

Nuclei, neighbouring nuclei

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5
Q

In NMR spectroscopy, the spinning nuclei in strong magnetic field must be irradiated by which of the following?

Perpendicular and stronger field
Perpendicular and weaker field
Parallel and stronger field
Parallel and weaker field

A

Perpendicular and weaker field

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6
Q

Interaction between matter and electromagnetic radiation can be observed by subjecting a substance to magnetic fields in which of the following manner?

Both fields should be stationary

Both fields should be varying

One field should be stationary and the other should be varying

It must be subjected to only one field

A

One field should be stationary and the other should be varying

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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?

Amplifier
Photodetector
GM counter
Radiofrequency detector

A

Radiofrequency detector

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8
Q

Which of the following are considered to be the lowest form of Electromagnetic radiation?

IR radiation
Micro waves
UV radiation
Radio waves

A

Radio waves

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9
Q

The amount of energy available in radio frequency radiation is sufficient for which of the following?

Excite an atom
Vibrate an atom
Vibrate a molecule
Affect the nuclear spin of an atom

A

Affect the nuclear spin of an atom

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10
Q

Nuclei having either the number of protons or neutrons as odd have _______ spin.

Integral spin
Half integral spin
Zero spin
Positive spin

A

Half integral spin

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11
Q

If the number of protons or neutrons is even the spin of the nucleus will be which of the following?

Integral spin
Half integral spin
Zero spin
Positive spin

A

Zero spin

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12
Q

The difference between the field necessary for resonance in the sample and in some arbitrary chosen compound is which of the following?

Field shift
Matrix effects
Chemical shift
Resonance shift

A

Chemical shift

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13
Q

Chemical shift allows a chemist to obtain the idea of how atoms are joined together.

True
False

A

True

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14
Q
  1. Elementary particles such as electrons and nucleus have the property of spin.

True
False

A

True

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15
Q
  1. Which of the following is not a type of NMR spectrometer?

Minimal type
Maximal type
Multipurpose type
Wideline type

A

Maximal type

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16
Q
  1. Which of the following NMR spectrometers have stressed reliability and ease of operation?

Minimal type
Maximal type
Multipurpose type
Wideline type

A

Minimal type

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17
Q

Which of the following type of NMR spectrometer uses a frequency synthesizer to generate RF fields?

Minimal type
Maximal type
Multipurpose type
Wideline type

A

Multipurpose type

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18
Q

In wideline NMR spectrometers, which of the following has to be supplied to the electromagnet?

Slowly varying low voltage
Rapidly varying low voltage
Slowly varying scan voltage
Rapidly varying scan voltage

A

Slowly varying scan voltage

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19
Q

Which among the following NMR spectrometer is the more diverse spectrometer?

Minimal type
Maximal type
Multipurpose type
Wideline type

A

Multipurpose type

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20
Q

Permanent magnet cannot be used in wideline type NMR spectrometer.

True
False

A

False

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21
Q

Which of the following NMR spectrometer emphasises on high performance versatility with cost being a secondary consideration?

Minimal type
Maximal type
Multipurpose type
Wideline type

A

Multipurpose type

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22
Q

Which of the following NMR spectrometer does not require power supply and cooling system?

Minimal type
Maximal type
Multipurpose type
Wideline type

A

Minimal type

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23
Q

Minimal type NMR spectrometer is inexpensive.

True
False

A

True

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24
Q

Which of the following is used as coolant for magnets in continuous-wave NMR spectrometer?

Water
Liquid He
Liquid Na
Heavy water

A

Water

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25
Q

Which of the following components are used to separate the nuclear spin energy states?

RF channels
Magnet
Sample probe
Sweep generator

A

Magnet

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26
Q
  1. In frequency sweep method, which of the following parameters are varied continuously?

Magnetic field
RF signal
Sample concentration
Amplification factor

A

RF signal

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27
Q

In field sweep method, which of the following parameters are varied continuously?

Magnetic field
RF signal
Sample concentration
Amplification factor

A

Magnetic field

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28
Q

Which of the following statements are not true about permanent magnets?

They are simple
They are inexpensive
They don’t require shielding
They don’t require power supply

A

They don’t require shielding

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29
Q

Which of the following is not true of electromagnets?

They are expensive
They require power supply
They don’t require cooling system
They don’t require extensive shielding

A

They don’t require cooling system

30
Q

For high resolution work the magnetic field over the entire sample volume must be maintained uniform in space and time.

True
False

A

True

31
Q

Which of the following must not be done to maintain the magnetic field over the sample uniform in space and time?

Large pole pieces need to be used
Pole faces must be polished
Wide pole gap must be present
Magnets can be permanent or electromagnet

A

Wide pole gap must be present

32
Q

The sample is contained in which of the following components?

Flask
Capillary tube
Curvette
Bore glass tube

A

Bore glass tube

33
Q

The single coil probe supplies the RF radiation to the sample and also serves as a part of which of the following circuits?

RF channels
Magnet
Detector
dSweep generator

A

Detector

34
Q

Nuclear induction probes’ one coil is used for signal detection. What is the function of the other coil?

Sample irradiation
Magnet
Detector
Sweep generator

A

Sample irradiation

35
Q

The voltage generated by the receiver coil is small and it must be amplified.

True
False

A

True

36
Q

The amplification required for continuous-wave NMR is of the order of which of the following?

10^1
10^2
10^3
10^5

A

10^5

37
Q

Which of the following can be used instead of magnets to produce the magnetic field?

Inductor
Motor
Generator
Superconducting solenoids

A

Superconducting solenoids

38
Q

How is the inhomogeneity of magnetic fields compensated?

With large magnetic fields
With small magnetic fields
By using two or more magnets
By providing required insulation

A

With small magnetic fields

39
Q

Fourier transform NMR spectrometer allows NMR transitions to be observed simultaneously.

True
False

A

True

40
Q

Fourier transform NMR spectrometer has which of the following characteristics?

Increased sensitivity, long time to obtain data
Decreased sensitivity, long time to obtain data
Increased sensitivity, reduced time to obtain data
Decreased sensitivity, reduced time to obtain data

A

Increased sensitivity, reduced time to obtain data

41
Q

Which of the following cannot be done due to the multiplex advantage?

Repetitive signals can be summed
Repetitive signals can be averaged
Increases signal to noise ratio
Decreases signal to noise ratio

A

Decreases signal to noise ratio

42
Q

Two coils are necessary in Fourier transform NMR spectroscopy.

True
False

A

False

43
Q

Which of the following is the disadvantage of conventional mode of spectrometer or continuous-wave NMR spectrometer?

They are unstable
Maintenance is difficult
High operating cost
Excitation is inefficient

A

Excitation is inefficient

44
Q

Which of the following must be done to improve sensitivity?

Frequency sweep mode must be preferred
Field sweep mode must be preferred
Single channel excitation must be preferred
Multichannel excitation must be preferred

A

Multichannel excitation must be preferred

45
Q

Which of the following is the disadvantage of multichannel excitation?

Low sensitivity
Low resolution
Small number of frequencies is present
Uneconomical

A

Uneconomical

46
Q

How can the need for array of narrow-band filters and detectors be eliminated?

By using multi-channel excitation
By using a detector for each frequency
By reducing the number of detectors
By using Fourier transform

A

By using Fourier transform

47
Q

Fourier transform can be accomplished by using which of the following components?

Spin decoder
Detector
Spectrum analyser
Oscilloscope

A

Spectrum analyser

48
Q

A 15.4 MHz crystal generates the _________ resonance frequency?

Hydrogen
Deuterium
Tritium
Helium

A

Deuterium

49
Q

Sensitivity is the ratio of peak signal amplitude to which of the following?

Time
Rms noise
Average noise
Peak-to-peak noise

A

Rms noise

50
Q

Which of the following is not an operating technique for sensitivity enhancement?

Optimization of sample volume
Optimization of instrumental parameters
Optimization of noise
Time averaging

A

Optimization of noise

51
Q

Which of the following techniques do not enhance sensitivity by a factor of 10 at normal operating conditions?

Optimization of sample volume
Optimization of instrumental parameters
Optimization of noise
Time averaging

A

Time averaging

52
Q

The most common spherical cells have which of the following dimensions?

4mm diameter
40mm diameter
8mm diameter
80mm diameter

A

4mm diameter

53
Q 
Better sensitivity with good resolution can be achieved by concentrating the sample inside which of the following?
Sample cell
Micro cell
Sample tube
Cylindrical tube
A

Micro cell

54
Q

Frequency spectrum of noise occupies a band that is _________ the signal spectrum. Choose the most appropriate option.

Narrow than
Wider than
Different from
Same as

A

Wider than

55
Q

Suppression of frequencies which contain no signal does which of the following?

Increases S/N ratio
Decreases S/N ratio
S/N ratio is kept constant
S/N ratio becomes 1

A

Increases S/N ratio

56
Q

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.

True
False

A

False

57
Q

Which of the following is not involved in signal averaging?

A system to repeatedly scan the spectral region of interest

Some storage device to store information

A system to coherently add individual spectra

Sweep generator

A

Sweep generator

58
Q

In order to have a long measuring time for increasing sensitivity, it is better to have several fast scans than a single slow scan.

True
False

A

True

59
Q

In Spin Decoupler, the output of the DC amplifier is applied to which of the following to control the power supplied to the oven heaters?

Power diode
Power transistor
Power MOSFET
Power IGBT

A

Power transistor

60
Q
  1. In Spin Decoupler, the difference frequency circuit provides a means of mixing two signals and a filter to recover which of the following?

Low-frequency component
High-frequency component
Low-voltage component
High-voltage component

A

Low-frequency component

61
Q

Mass spectrometers are used to determine which of the following?

Composition in sample
Concentration of elements in sample
Relative mass of atoms
Properties of sample

A

Relative mass of atoms

62
Q
  1. Who invented mass spectrometers?

J.J Thompson
Goldstein
Nikola Tesla
Aston

A

J.J Thompson

63
Q

In mass spectrometer, the sample that has to be analysed is bombarded with which of the
following?

Protons
Electrons
Neutrons
Alpha particles

A

Electrons

64
Q

Mass spectrometer separates ions on the basis of which of the following?

Mass
Charge
Molecular weight
Mass to charge ratio

A

Mass to charge ratio

65
Q

In mass spectrometer, the ions are sorted out in which of the following ways?

By accelerating them through electric field
By accelerating them through magnetic field
By accelerating them through electric and magnetic field
By applying a high voltage

A

By accelerating them through electric and magnetic field

66
Q

No two molecules will be fragmented and ionized in exactly the same manner.

True
False

A

True

67
Q

The procedure for mass spectroscopy starts with which of the following processes?

The sample is bombarded by electron beam

The ions are separated by passing them into electric and magnetic field

The sample is converted into gaseous state

The ions are detected

A

The sample is converted into gaseous sta

68
Q

In mass spectrometer, the ion currents are measured using which of the following?

Scintillation counter
Ion counter
Electrometer tube
Electric fields

A

Electrometer tube

69
Q

Which of the following ions pass through the slit and reach the collecting plate?

Negative ions of all masses
Positive ions of all masses
Negative ions of specific mass
Positive ions of specific mass

A

Positive ions of specific mass

70
Q

Which of the following statements is not true about mass spectrometry?

Impurities of masses different from the one being analysed interferes with the result

It has great sensitivity

It is suitable for data storage

It is suitable for library retrival

A

Impurities of masses different from the one being analysed interferes with the resul

71
Q

In mass spectrometer, the sample gas is introduced into the highly evacuated spectrometer tube and it is ionised by electron beam.

True
False

A

True

72
Q

end

A

end

ANAL CHEM (5 decks)

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