Instrumental Methods for Chemical Analysis

Atomic absorption spectrophotometer

1. Which of the following is the principle of Atomic Absorption Spectroscopy?

a) Radiation is absorbed by non-excited atoms in vapour state and are excited to higher states

b) Medium absorbs radiation and transmitted radiation is measured

c) Colour is measured

d) Colour is simply observed

Answer: Radiation is absorbed by non-excited atoms in vapour state and are excited to higher states

2. In Atomic Absorption Spectroscopy, which of the following is the generally used radiation source?

a) Tungsten lamp

b) Xenon mercury arc lamp

c) Hydrogen or deuterium discharge lamp

d) Hollow cathode lamp

Answer: Hollow cathode lamp

3. In Atomic Absorption Spectroscopy, with what material is the cathode in Hollow cathode lamp constructed?

a) Tungsten

b) Quartz

c) Element to be investigated

d) Aluminium

Answer: Element to be investigated

4. How can the intensity of radiation be increased in Hollow cathode lamp?

a) Addition of non-conductive protective shield of mica

b) Addition of nitrogen to neon or argon in the lamp

c) Increasing the pressure of the filling gas

d) Changing the metal of the anode

Answer: Addition of non-conductive protective shield of mica

5. Which of the following is the function of the chopper in Atomic Absorption Spectroscopy?

a) To split the beam into two

b) To break the steady light into a pulsating light

c) To filter unwanted components

d) To reduce the sample into atomic state

Answer: To break the steady light into a pulsating light

6. Which of the following is the function of the Flame or Emission system in Atomic Absorption Spectroscopy?

a) To split the beam into two

b) To break the steady light into pulsating light

c) To filter unwanted components

d) To reduce the sample into atomic state

Answer: To reduce the sample into atomic state

7. Atomic absorption spectroscopy is also called as Absorption Flame Photometry.

a) True

b) False

Answer: True

8. Which of the following is not a component of the emission system in Flame photometer?

a) Burner

b) Atomiser

c) Fuel gases and their regulation

d) Chopper

Answer: Chopper

9. Which of the following is the function of the atomiser in the emission system of Atomic Absorption Spectroscopy?

a) To split the beam into two

b) To break the steady light into pulsating light

c) To break large mass of liquid into small drops

d) To reduce the sample into atomic state

Answer: To break large mass of liquid into small drops

10. Which of the following is not a fuel used in flame photometry?

a) Acetylene

b) Propane

c) Hydrogen

d) Camphor oil

Answer: Camphor oil

11. Which of the following is not the requirement of a good flame in flame photometer?

a) Liquid sample must be evaporated to form solid residue

b) Solid residue must decompose to form atoms

c) Atoms must be produced such that they have the ability to get excited to higher states

d) Atoms must be produced such that they are in stable state

Answer: Atoms must be produced such that they are in stable state

12. Atomic Absorption Spectroscopy is used for the analysis of metals.

a) True

b) False

Answer: True

13. Which of the following options explains the process of ‘sputtering’ that occurs in Hollow Cathode Lamp?

a) Positive ions collide with cathode surface and metal atoms from cathode are ejected

b) Negative ions collide with cathode surface and metal atoms from anode are ejected

c) Positive ions collide with negative ions and metal atoms from anode are ejected

d) Positive ions collide with negative ions and photons are ejected

Answer: Positive ions collide with cathode surface and metal atoms from cathode are ejected

14. At what pressure should the gases in the sealed tube be maintained in the Hollow cathode lamp?

a) 1 to 5 torr

b) 20 to 30 torr

c) 40 to 50 torr

d) 50 to 55 torr

Answer: 1 to 5 torr

UV-visible spectrophotometers

1. Beer Lambert’s law gives the relation between which of the following?

a) Reflected radiation and concentration

b) Scattered radiation and concentration

c) Energy absorption and concentration

d) Energy absorption and reflected radiation

Answer: Energy absorption and concentration

2. In which of the following ways, absorption is related to transmittance?

a) Absorption is the logarithm of transmittance

b) Absorption is the reciprocal of transmittance

c) Absorption is the negative logarithm of transmittance

d) Absorption is a multiple of transmittance

Answer: Absorption is the negative logarithm of transmittance

3. Which of the following is not a limitation of Beer Lambert’s law, which gives the relation between absorption, thickness and concentration?

a) Concentration must be lower

b) Radiation must have higher bandwidth

c) Radiation source must be monochromatic

d) Does not consider factors other than thickness and concentration that affect absorbance

Answer: Radiation must have higher bandwidth

4. Beer’s law states that the intensity of light decreases with respect to ___________

a) Concentration

b) Distance

c) Composition

d) Volume

Answer: Concentration

5. Lambert’s law states that the intensity of light decreases with respect to __________

a) Concentration

b) Distance

c) Composition

d) Volume

Answer: Distance

6. The representation of Beer Lambert’s law is given as A = abc. If ‘b’ represents distance, ‘c’ represents concentration and ‘A’ represents absorption, what does ‘a’ represent?

a) Intensity

b) Transmittance

c) Absorptivity

d) Admittance

Answer: Absorptivity

7. Which of the following is not true about Absorption spectroscopy?

a) It involves transmission

b) Scattering is kept minimum

c) Reflection is kept maximum

d) Intensity of radiation leaving the substance is an indication of a concentration

Answer: Reflection is kept maximum

8. Transmittance is given as T = P/Po. If Po is the power incident on the sample, what does P represent?

a) Radiant power transmitted by the sample

b) Radiant power absorbed by the sample

c) Sum of powers absorbed and scattered

d) Sum of powers transmitted and reflected

Answer: Radiant power transmitted by the sample

9. What is the unit of absorbance which can be derived from Beer Lambert’s law?

a) L mol-1 cm-1

b) L gm-1 cm-1

c) Cm

d) No unit

Answer: No unit

10. What is the unit of molar absorptivity or absorptivity which is used to determine absorbance A in Beer Lambert’s formula?

a) L mol-1 cm-1

b) L gm-1 cm-1

c) Cm

d) No unit

Answer: L mol-1 cm-1

single and double beam instruments

1. Which of the following statements is false about single beam absorption instruments?

a) Tungsten bulb is used as a source

b) Beam splitter is used to get parallel beam

c) Test tube is used as sample holder

d) Photovoltaic cell as detector

Answer: Beam splitter is used to get parallel beam

2. Which of the following statement is false about double beam absorption instruments?

a) It is similar to single beam instruments except two beams are present

b) Tungsten bulb is used as a source

c) Reference beam must have a higher intensity than sample beam

d) Both the beams after they pass through respective samples are compared

Answer: Reference beam must have a higher intensity than sample beam

3. Which of the following is not an application of colorimeter?

a) Paints

b) Inks

c) Cosmetics

d) Composition detection

Answer: Composition detection

4. In photometers, the readings of the specimen are initially obtained in the form of which of the following parameters?

a) Transmittance

b) Absorption

c) Wavelengths

d) Volume

Answer: Transmittance

5. Colorimeters are used in applications where great accuracy is required.

a) True

b) False

Answer: False

6. Colorimeters are used to determine the concentration of solutions.

a) True

b) False

Answer: True

7. Which of the following is the purpose of balance indicator in double beam photometer or colorimeter?

a) Selects a particular wavelength

b) Splits the wavelength selected into two equal beams

c) Detects and indicates the amount of light falling on it

d) Indicates the difference between the output of two photometers

Answer: Indicates the difference between the output of two photometers

8. Which of the following is the purpose of the beam splitter in double beam photometer or colorimeter?

a) Splits beam into two equal intensity beams

b) Splits beam in such a way that sample beam has higher intensity

c) Splits beam in such a way that a reference beam has higher intensity

d) Merge two equal intensity beams into single beam

Answer: Splits beam into two equal intensity beams

9. Which of the following is a source used in spectroscopy?

a) LASER

b) Tube light

c) Sodium vapour lamp

d) Tungsten lamp

Answer: Tungsten lamp

Instrumentation of IR

1. Which of the following is not a source used in Mid Infrared Spectrophotometer?

a) Nernst glower

b) High pressure mercury arc lamp

c) Globar

d) Nichrome wire

Answer: High pressure mercury arc lamp

2. Which of the following is the wave number of near infrared spectrometer?

a) 4000 – 200 cm-1

b) 200 – 10 cm-1

c) 12500 – 4000 cm-1

d) 50 – 1000 cm-1

Answer: 12500 – 4000 cm-1

3. Which of the following options are correct in terms of wavelength for the different types of IR spectrometer?

a) Near IR: 0.8 – 2.5 mm

b) Mid IR: 0.8 – 2.5 mm

c) Far IR: 2.5 – 50 mm

d) Mid IR: 50 – 100 mm

Answer: Near IR: 0.8 – 2.5 mm

4. Which of the following is not a composition of Nernst glower or Nernst filament?

a) Oxides of Zirconium

b) Oxides of Barium

c) Oxides of Yitrium

d) Oxides of Thorium

Answer: Oxides of Barium

5. What is the composition of Globar rod which is used as a source in Mid IR spectroscopy?

a) Silicon carbide

b) Silver chloride

c) Silicon dioxide

d) Silver carbide

Answer: Silicon carbide

6. Bolometer, a type of detector, is also known as ___________

a) Resistance temperature detector (RTD)

b) Thermistor

c) Thermocouple

d) Golay cell

Answer: Thermistor

7. Which of the following is not a technique for preparing solid samples in IR spectroscopy?

a) Solids run in solution

b) Mull technique

c) Solid films

d) Thin films

Answer: Thin films

8. Which of the following is not used as pyroelectric material used in pyroelectric transducers in Infrared spectroscopy?

a) Triglycine Sulphate

b) Deutrated Triglycine Sulphate

c) Some Polymers

d) Tetraglycine sulphate

Answer: Tetraglycine sulphate

9. Which of the following is the principle of Golay cell which is used as a detector in IR spectroscopy?

a) Expansion of gas upon heating

b) Increase in resistance due to an increase in temperature and vice versa

c) Temperature difference gives rise to a potential difference in the material

d) Decrease in resistance due to an increase in temperature

Answer: Expansion of gas upon heating

10. In a solid sample treatment technique, the finely ground solid sample is mixed with mineral oil to make a thick paste which is then spread between IR transmitting windows. What is the name of this solid sample treatment technique?

a) Pressed pellet

b) Mull technique

c) Solid films

d) Solids run in solution

Answer: Mull technique

Fourier Transform Infra-red Spectrometers

1. Which of the following is not true about Fourier Transform Infrared (FTIR) spectrometer?

a) It is of non-dispersive type

b) It is useful where repetitive analysis is required

c) Size has been reduced over the years

d) Size has increased over the years

Answer: Size has increased over the years

2. In the most widely used beam splitter, a thin film of ________ is sandwiched between two plates of low refractive index solid. Fill the blank with a suitable option.

a) Mylar

b) Silicon carbide

c) Ferrous oxide

d) Silver chloride

Answer: Mylar

3. Which of the following is not the function of the drive mechanism in Fourier Transform Infrared Spectrophotometer?

a) Movement of mirror to obtain a satisfactory interferogram

b) Acquire a good interferogram pattern

c) Allow 50% of the beam to pass

d) Keep the speed of the moving mirror constant

Answer: Allow 50% of the beam to pass

4. Only pyroelectric transducer or pyroelectric crystals are used as detectors in Fourier Transform Infrared Spectrophotometer (FTIR). What is the main reason for other types of thermal detectors are not being used in FTIR spectrophotometer?

a) Less accuracy

b) Slower response

c) Less precision

d) Less sensitivity

Answer: Slower response

5. Which of the following is not the advantage of Fourier Transform Spectrometers?

a) Signal to noise ratio is high

b) Information could be obtained on all frequencies

c) Retrieval of data is possible

d) Easy to maintain

Answer: Easy to maintain

6. Which of the following has to be computed to determine transmittance and absorbance at various frequencies?

a) Ratio of signal and noise

b) Ratio of sample and reference spectra

c) Sample spectra

d) Reference spectra

Answer: Ratio of sample and reference spectra

7. Computer accepts analog signals directly.

a) True

b) False

Answer: False

8. Which of the following is the reference that is generally used in FTIR interferometer?

a) Air

b) NaCl solution

c) Alcohol

d) Base solution

Answer: Air

9. In Michelson Interferometer, if the reflected and transmitted beams are in phase at the beam splitter, then maximum intensity will reach the detector.

a) True

b) False

Answer: True

10. In Michelson’s interferometer, the frequency of the detector output can be determined by translating the _________ of movable mirror and the ___________ of monochromatic radiation.

a) Velocity, wavelength

b) Thickness, intensity

c) Length, velocity

d) Angle, intensity

Answer: Velocity, wavelength

11. In Michelson’s interferometer, the __________ of the detector output will depend upon the intensity of incoming radiation.

a) Velocity

b) Frequency

c) Amplitude

d) Phase

Answer: Amplitude

12. Why is the computer necessary in Fourier Transform Spectrometer?

a) To display the detector output

b) To process the detector output

c) To determine the amplitude

d) To determine the frequency

Answer: To process the detector output

Flame Emission Photometers

1. The function of pressure regulators in the emission system of flame photometer is to have a steady flame which is free from flickers.

a) True

b) False

Answer: True

2. In Total consumption burner, only samples of particular droplet size will enter the burner.

a) True

b) False

Answer: False

3. Which of the following is the principle of Flame emission photometers?

a) Radiation is absorbed by non-excited atoms in vapour state and are excited to higher states

b) Medium absorbs radiation and transmitted radiation is measured

c) Colour and wavelength of the flame is measured

d) Only wavelength of the flame is measured

Answer: Colour and wavelength of the flame is measured

4. In Flame emission photometers, the measurement of _____________ is used for qualitative analysis.

a) Colour

b) Intensity

c) Velocity

d) Frequency

Answer: Colour

5. In Flame emission photometers, the measurement of _____________ is used for quantitative analysis.

a) Colour

b) Intensity

c) Velocity

d) Frequency

Answer: Intensity

6. Which of the following is not an advantage of Laminar flow burner used in Flame photometry?

a) Noiseless

b) Stable flame for analysis

c) Efficient atomization of sample

d) Sample containing two or more solvents can be burned efficiently

Answer: Sample containing two or more solvents can be burned efficiently

7. Laminar flow burner used in Flame photometers is also known as ____________

a) Turbulent burner

b) Premix burner

c) Total consumption burner

d) Nozzle mix burner

Answer: Premix burner

8. Which of the following is the advantage of prism monochromators?

a) Dispersion is non-overlapping

b) Dispersion occurs in non-linear manner

c) Dispersion is overlapping

d) Dispersion occurs in a linear manner

Answer: Dispersion is non-overlapping

9. Which of the following is the advantage of grating monochromators?

a) Dispersion is non-overlapping

b) Dispersion occurs in non-linear manner

c) Dispersion is overlapping

d) Dispersion occurs in a linear manner

Answer: Dispersion occurs in a linear manner

10. Which of the following is not a detector used in Flame emission photometers?

a) Photronic cell

b) Photovoltaic cell

c) Photoemissive tube

d) Chromatogram

Answer: Chromatogram

11. Phototubes are more sensitive than photovoltaic cells.

a) True

b) False

Answer: True

12. Which of the following is not an application of Flame emission photometers?

a) Analysis of biological fluids

b) Determination of sodium, potassium in soil

c) Determination of metals such as Mn, Cu

d) Analysis of complex mixtures

Answer: Analysis of complex mixtures

13. Which of the following is not an advantage of a photovoltaic cell which is used as a detector in Flame emission photometers?

a) Portable

b) No external supply

c) Robust in construction

d) Does not show fatigue

Answer: Does not show fatigue

Nuclear Magnetic Resonance (NMR) spectrometry

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

Answer: Liquids

2. 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

Answer: Radio frequency radiation

3. 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

Answer: Accurate, non-destructive

4. 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

Answer: Nuclei, neighbouring nuclei

5. 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

Answer: Perpendicular and weaker field

6. 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

Answer: One field should be stationary and the other should be varying

7. 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

Answer: Radiofrequency detector

8. 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

Answer: Radio waves

9. 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

Answer: Affect the nuclear spin of an atom

10. 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

Answer: Half integral spin

11. 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

Answer: Zero spin

12. 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

Answer: Chemical shift

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

a) True

b) False

Answer: True

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

a) True

b) False

Answer: True

Types of NMR Spectrometers

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

a) Minimal type

b) Maximal type

c) Multipurpose type

d) Wideline type

Answer: Maximal type

2. 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

Answer: Minimal type

3. 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

Answer: Multipurpose type

4. 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

Answer: Slowly varying scan voltage

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

a) Minimal type

b) Maximal type

c) Multipurpose type

d) Wideline type

Answer: Multipurpose type

6. Permanent magnet cannot be used in wideline type NMR spectrometer.

a) True

b) False

Answer: False

7. 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

Answer: Multipurpose type

8. 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

Answer: Minimal type

9. Minimal type of NMR spectrometer is inexpensive.

a) True

b) False

Answer: True

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

Answer: Water

Continuous Wave NMR Spectroscopy

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

Answer: Magnet

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

Answer: RF signal

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

Answer: Magnetic field

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

Answer: They don’t require shielding

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

Answer: They don’t require a cooling system

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

Answer: True

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

Answer: Wide pole gap must be present

8. The sample is contained in which of the following components?

a) Flask

b) Capillary tube

c) Curvette

d) Bore glass tube

Answer: Bore glass tube

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

Answer: Detector

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

Answer: Sample irradiation

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

a) True

b) False

Answer: True

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

a) 101

b) 102

c) 103

d) 105

Answer: 105

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

a) Inductor

b) Motor

c) Generator

d) Superconducting solenoids

Answer: Superconducting solenoids

14. 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

Answer: With small magnetic fields

Fourier Transform NMR Spectroscopy

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

a) True

b) False

Answer: True

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

Answer: Increased sensitivity, reduced time to obtain data

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

Answer: Decreases signal to noise ratio

4. Two coils are necessary for Fourier transform NMR spectroscopy.

a) True

b) False

Answer: False

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

Answer: Excitation is inefficient

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

Answer: Multichannel excitation must be preferred

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

Answer: Uneconomical

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

Answer: By using Fourier transform

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

a) Spin decoder

b) Detector

c) Spectrum analyser

d) Oscilloscope

Answer: Spectrum analyser

10. A 15.4 MHz crystal generates the _________ resonance frequency.

a) Hydrogen

b) Deuterium

c) Tritium

d) Helium

Answer: Deuterium

Sensivity Enhancement for NMR Spectroscopy

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

Answer: Rms noise

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

Answer: Optimization of noise

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

Answer: Time averaging

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

a) 4mm diameter

b) 40mm diameter

c) 8mm diameter

d) 80mm diameter

Answer: 4mm diameter

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

Answer: Micro cell

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

Answer: Wider than

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

Answer: Increases S/N ratio

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

Answer: False

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

Answer: Sweep generator

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

Answer: True

11. 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?

a) Power diode

b) Power transistor

c) Power MOSFET

d) Power IGBT

Answer: Power transistor

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

a) Low-frequency component

b) High-frequency component

c) Low-voltage component

d) High-voltage component

Answer: Low-frequency component

Gas analysers

Paramagnetic Oxygen Analyser

1. Which among the following gases have diamagnetic property (ability to be repelled by magnetic fields)?

a) Oxygen

b) Nitrogen

c) Nitrogen dioxide

d) Nitric oxide

Answer: Nitrogen

2. Which of the following gases have paramagnetic property (ability to get attracted to a magnetic field)?

a) Nitric oxide

b) Hydrogen

c) Helium

d) Nitrogen

Answer: Nitric oxide

3. The force produced during the operation of Paramagnetic oxygen analyzer is proportional to which of the following?

a) Magnetic susceptibility of sphere

b) Magnetic susceptibility of surrounding gas

c) Difference between magnetic susceptibility of sphere and magnetic field strength

d) Difference between magnetic susceptibility of sphere and that of surrounding gas

Answer: Difference between magnetic susceptibility of sphere and that of surrounding gas

4. In Paramagnetic oxygen analyzer, the expression for magnitude of force produced can be expressed as, F = C (K-KO), where K= magnetic susceptibility of surrounding gas and KO= magnetic susceptibility of sphere. C denotes which of the following?

a) Magnetic field strength

b) Magnetic gradient

c) Function of magnetic field strength and gradient

d) Magnetic flux

Answer: Function of magnetic field strength and gradient

5. In Paramagnetic oxygen analyzer, the electrostatic force that is exerted should have which of the following features?

a) It should be greater than the magnetic field and must be in the same direction

b) It should be equal to the magnetic field and must be in the same direction

c) It should be greater than the magnetic field and must be in the opposite direction

d) It should be equal to the magnetic field and must be in the opposite direction

Answer: It should be equal to the magnetic field and must be in the opposite direction

6. Which of the following is true about the two charged vanes that produce electric field in Paramagnetic oxygen analyzer?

a) Both the vanes should be at higher potential than the test body

b) Both the vanes should have the same potential as the test body

c) One vane should be at higher potential than the test body and the other vane should be at lower potential

d) Both the vanes should be at lower potential than the test body

Answer: One vane should be at higher potential than the test body and the other vane should be at lower potential

7. In Paramagnetic oxygen analyzer, when no oxygen is present the magnetic force balances torque of the fibre.

a) True

b) False

Answer: True

8. To improve paramagnetic oxygen analyzer, the quartz suspension must be replaced with which of the following?

a) Platinum-iridium

b) Phosphor-bronze

c) Gold-palladium

d) Antimony

Answer: Platinum-iridium

9. In the Beckman instrument, the flow rate recommended when the sample enters through a porous diffusion disc is which of the following?

a) 100-200 cc/min

b) 50-250 cc/min

c) 40-60 cc/min

d) 200-300 cc/min

Answer: 50-250 cc/min

10. In the Beckman instrument, the flow rate recommended when the sample enters directly for rapid response is which of the following?

a) 100-200 cc/min

b) 50-250 cc/min

c) 40-60 cc/min

d) 200-300 cc/min

Answer: 40-60 cc/min

11. Which of the following happens to the magnetic susceptibility of gases when the temperature changes?

a) It increases with increase in temperature

b) It decreases with increase in temperature

c) It remains constant with increase in temperature

d) It remains constant with decrease in temperature

Answer: It decreases with increase in temperature

12. If the oxygen content is not greater than 21%, which of the following gases must be used to set the span point?

a) Oxygen

b) Dry air

c) Nitrogen

d) Hydrogen

Answer: Dry air

13. If the oxygen content is greater than 21%, which of the following gases must be used to set the span point?

a) Oxygen

b) Dry air

c) Nitrogen

d) Hydrogen

Answer: Oxygen

Electrochemical Methods for Oxygen Analysis

1. Which of the following is not true about the galvanic method of oxygen analysis?

a) Electrodes are composed of noble and base metals

b) It can measure dissolved content of oxygen

c) Its principle is based on electrolysis

d) It utilizes an electronic cell

Answer: Its principle is based on electrolysis

2. Which of the following is true about Hersch cell which is one of the arrangements of a galvanic cell?

a) Cell is spherical in shape

b) Cathode is made of porous material

c) Cathode is placed centrally

d) Cathode is formed by gauze which surrounds the anode

Answer: Cathode is formed by gauze which surrounds the anode

3. Polarographic cells type of electrochemical method uses which of the following concepts?

a) Cyclic reactions

b) Exothermic reactions

c) Reversible reactions

d) Redox reactions

Answer: Redox reactions

4. Which of the following methods, is the widely used method for trace gas analysis?

a) Galvanic methods

b) Conductometric method

c) Polarographic cells

d) Thermal conductivity method

Answer: Conductometric method

5. In the conductometric method, the difference in gas conductivity before and after passing sample gas denotes which of the following?

a) Efficiency of the cell

b) Quantity of reagent

c) Concentration of gas

d) Density of the reagent

Answer: Concentration of gas

6. Conductometric method is not very suitable for measuring traces of which of the following gases in ppb range?

a) H2S

b) SO2

c) NH3

d) CO

Answer: CO

7. Polarographic cells are not sensitive to which of the following gases?

a) Carbon monoxide

b) Carbon dioxide

c) Nitrous oxide

d) Oxygen

Answer: Carbon monoxide

8. In polarographic cell when potential is applied, oxygen is reduced at __________ when KCl is present.

a) Anode

b) Cathode

c) Electrolyte

d) Both the electrode

Answer: Cathode

9. Polarographic cells are used to measure the partial pressure of gases only in static gas monitoring systems and not in continuous streams.

a) True

b) False

Answer: False

10. Polarographic cells used for measuring the partial pressure of oxygen are temperature-sensitive.

a) True

b) False

Answer: True

NO2 Analyser

1. Nitrogen dioxide can be detected with a paramagnetic analyser.

a) True

b) False

Answer: True

2. Nitrogen oxide cannot be directly analysed using UV and Visible analyzers due to which of the following reasons?

a) Less accuracy

b) Very low range

c) It leads to contamination of the sample

d) It is transparent in UV visible regions

Answer: It is transparent in UV visible regions

3. How is NO converted to NO2 for analysis in UV and Visible analyzers?

a) Treating sample gas with pressurized oxygen

b) Treating sample gas with ozone

c) Treating sample gas with oxygen at low pressure

d) Treating sample gas with water at high pressure

Answer: Treating sample gas with pressurized oxygen

4. How is NO converted to NO2 for analysis in Chemiluminescent analyser?

a) Treating sample gas with pressurized oxygen

b) Treating sample gas with ozone

c) Treating sample gas with oxygen at low pressure

d) Treating sample gas with water at high pressure

Answer: Treating sample gas with ozone

5. During analysis of NO2 using Chemiluminescent analyser, why is NO2 not made to react with ozone directly?

a) Less accuracy

b) It is a slow process

c) It leads to contamination of the sample

d) It does not produce luminescence

Answer: It is a slow process

8. The instruments based on chemiluminescence maintain linearity in which of the following ranges?

a) 1ppb to 100ppb

b) 100ppb to 1000ppb

c) 1ppb to 1000ppb

d) 100ppb to 1000ppb

Answer: 1ppb to 1000ppb

9. In Laser Opto-acoustic spectroscopy, the IR beam excites the molecules to higher states. In which of the following ways do the molecules return to the ground state?

a) Collisional de-excitation

b) Random de-excitation

c) By spontaneous emission

d) By stimulated emission

Answer: Collisional de-excitation

10. Which of the following detectors are generally used for detection in NO analysis using CO laser?

a) Photomultiplier tube

b) Photovoltaic cell

c) Liquid nitrogen cooled Ge-Au element

d) Photo emissive tube

Answer: Liquid nitrogen cooled Ge-Au element

11. Which of the following analyzers are used to measure trace amounts of nitrogen oxides in the stratosphere?

a) Chemiluminescence

b) CO laser method

c) Laser opto-acoustic spectroscopy

d) Colorimetry

Answer: Laser opto-acoustic spectroscopy

12. A pink coloured dye complex is formed when air containing NO2 is passed in an absorbing solution consisting of __________ and diamine dissolved in the acetic acid medium.

a) Sulphuric acid

b) Sulphonyl

c) Sulphonic acid

d) Sulphanilic acid

Answer: Sulphanilic acid

13. To monitor oxides of nitrogen in stack effluents, the sample containing oxides of nitrogen is passed through a flask containing solution of H2O2 in sulphuric acid. Nitric acid is formed. The nitrate ions then react with phenol-disulphonic acid to produce blue colour.

a)True

b) False

Answer: False

14. How can absorption be enhanced while determining NO concentration using CO laser?

a) By converting NO into NO2

b) By placing NO in a magnetic field

c) By using proper monochromators

d) By using choppers

Answer: By placing NO in a magnetic field