Industrial Gas Analysers Multiple Choice Questions and Answers

Industrial Gas Analysers Multiple Choice Questions and Answers

1. 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.

2. 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.

3. 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.

4. Which among the following gases have ability to be repelled by magnetic fields?
a) Oxygen
b) Nitrogen
c) Nitrogen dioxide
d) Nitric oxide
Answer: Nitrogen.

5. 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.

6. 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.

7. Which of the following gases have ability to get attracted to a magnetic field?
a) Nitric oxide
b) Hydrogen
c) Helium
d) Nitrogen
Answer: Nitric oxide.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. Sample rates of nitrogen meter can be adjusted by doing which of the following?
a) By modifying the amplifier
b) With the help of the needle valve
c) By modifying the detector
d) By changing chopper frequency
Answer: With the help of the needle valve.

16. Gases emit radiation under which of the following conditions which can be used for determination of gases?
a) When mixed with other gases
b) When kept at suitable temperature
c) With sufficient electrical excitation and at suitable pressures
d) When exposed to radiation
Answer: With sufficient electrical excitation and at suitable pressures.

17. In which of the following ways can nitrogen be calibrated for dry gases?
a) By modifying the amplifier
b) By adjusting the needle valve
c) By modifying the detector
d) By changing chopper frequency
Answer: By adjusting the needle valve.

18. Which of the following measuring technique is utilized for measuring nitrogen?
a) By using a method based on gas density
b) By using paramagnetic analyzers
c) By using magnetic wind instruments
d) By using a photospectrometer where a gas sample is analysed and detected with a photocell
Answer: By using a photospectrometer where a gas sample is analysed and detected with a photocell.

19. Nitrogen meters are calibrated for which of the following to measure nitrogen?
a) Mixture of nitrogen and air
b) Water saturated mixture of nitrogen and oxygen
c) Mixture of nitrogen and hydrogen
d) Nitrogen
Answer: Water saturated mixture of nitrogen and oxygen.

20. The characteristic emission of which colour, when discharge takes place in a low pressure chamber containing gas sample, will indicate the presence of nitrogen while using photospectrometer?
a) Purple
b) Blue
c) Pink
d) Green
Answer: Purple.

21. Which of the following is the normal sampling rate used in nitrogen meters?
a) 13 ml/min
b) 33 ml/min
c) 3 ml/min
d) 43 ml/min
Answer: 3 ml/min.

22. Why is nitrogen meters generally not calibrated for dry gases while measuring nitrogen?
a) It causes error
b) Range decreases
c) Reading tend to be non-linear
d) It cannot be measured
Answer: It causes error.

23. Which of the following occurs in Electrochemical cells used for the detection of hydrogen sulphide?
a) Change in resistance
b) Redox reaction
c) Oxidation-reduction reaction
d) Change in colour
Answer: Oxidation-reduction reaction.

24. Which of the following is not an advantage of electrochemical cells used for analysis of H2S?
a) Portable battery operated instrument
b) Pocket sized instrument
c) No pumps are needed
d) No interference from background gases
Answer: No interference from background gases.

25. Which of the following is not an advantage of solid state sensor used for analysis of H2S?
a) No sampling system
b) It can be used in conditions involving vibration
c) It can be used in corrosive atmosphere
d) No interference from background gases
Answer: No interference from background gases.

26. Which of the following methods is not used for detection of hydrogen sulphide?
a) Lead acetate tape staining method
b) Solid state sensor
c) Chemiluminescence method
d) Electrochemical cells
Answer: Chemiluminescence method.

27. Which is the compound that forms the stain in Lead Acetate Tape Staining method used for the analysis of Hydrogen Sulphide and what is the colour of the stain?
a) Lead Sulphide, red colour
b) Lead Sulphide, brown colour
c) Hydrogen acetate, white colour
d) Hydrogen acetate, green colour
Answer: Lead Sulphide, brown colour.

28. In solid state sensor, when heated to 150o to 300o which of the following occurs?
a) Resistance decreases with increase in H2S concentration
b) Resistance increases with H2S concentration
c) No change in resistance occurs
d) Sensor does not respond in this temperature range
Answer: Resistance decreases with increase in H2S concentration.

29. Which of the following is not a component of solid state sensor used for detection of hydrogen sulphide?
a) Heater
b) Thermistor
c) Semiconductor film
d) Photo detector
Answer: Photo detector.

30. Which of the following methods are mainly used in combustible gas detection equipment?
a) Lead acetate tape staining method
b) Solid state sensor
c) Gold film sensor
d) Electrochemical cells
Answer: Solid state sensor.

31. 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.

32. 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.

33. 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.

34. 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.

35. 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.

36. 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.

37. 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

38. In which of the following conditions can thermal conductivity analyzer be used for multi-component mixtures?
a) When all the components have same thermal conductivities
b) When all the components have very different thermal conductivities
c) When all but one component have same thermal conductivities
d) When all components have very different thermal conductivities except two of them which are the same
Answer: When all but one component have same thermal conductivities.

39. Thermal conductivity analyzers cannot be used in which of the following measurements?
a) Hydrogen in blast furnace gases
b) Determination of argon in oxygen in the process of air decomposition
c) Sulphur dioxide in roasting gases in production of sulphuric acid
d) Oxygen from a mixture of oxygen and nitrogen
Answer: Oxygen from a mixture of oxygen and nitrogen.

40. Which among the following elements has the highest thermal conductivity?
a) Nitrogen
b) Oxygen
c) Hydrogen
d) Chlorine
Answer: Hydrogen

41. Which of the following is not the characteristic of thermistors used in thermal conductivity analyzers?
a) High negative temperature coefficient of resistance
b) Slow response
c) Extremely sensitive
d) Low cost
Answer: Slow response.

42. Which of the following is generally used as indicators in bridges in thermal conductivity analyzers?
a) Voltmeter
b) Ammeter
c) Galvanometer
d) Wattmeter
Answer: Galvanometer.

43. How can the high speed of response be obtained in thermal conductivity analyzers?
a) By increasing the pressure of gas surrounding the filaments
b) By reducing the pressure of gas surrounding the filaments
c) By reducing the temperature of gas surrounding the filaments
d) By increasing the temperature of gas surrounding the filaments
Answer: By reducing the pressure of gas surrounding the filaments.

44. Which of the following materials are generally not used for the construction of filaments in thermal conductivity analyzers?
a) Tungsten
b) Gold
c) Platinum
d) Kovar
Answer: Gold.

45. Which of the following bridges are used in thermal conductivity analyzers?
a) Wheatstone bridge
b) Kelvin’s bridge
c) Anderson’s bridge
d) Schering’s bridge
Answer: Wheatstone bridge.

46. Which of the following is the relationship between the density of ideal gas and its molecular weight?
a) Directly proportional
b) Inversely proportional
c) Linear
d) No relation
Answer: Linear.

47. Which of the following detectors are not used in analyzers based on gas density?
a) Hot wire
b) Platinum filament
c) Thermistor
d) Thermometer
Answer: Thermometer.

48. Under which of the following conditions do all real gases behave as ideal gases to some extent?
a) Low temperature and low pressure
b) Low temperature and high pressure
c) High temperature and low pressure
d) Room temperature and normal pressure
Answer: Room temperature and normal pressure.

49. When would the recorder indicate a zero base line in analyzers based on gas density?
a) When the detector on the sample side is cooler than that on the reference side
b) When the detector on the reference side is cooler than that on the sample side
c) When flow is unbalanced
d) When both the detectors are equally cooled
Answer: When both the detectors are equally cooled.

50. Which of the following is the effective sample volume in analyzers based on gas density?
a) 10 ml
b) 20 ml
c) 5 ml
d) 50 ml
Answer: 5 ml

51. In analyzers based on gas density, the unbalance of the bridge is linearly proportional to which of the following?
a) Temperature of sample detector
b) Pressure at sample detector
c) Pressure difference between both the detectors
d) Gas-density difference between both the detectors
Answer: Gas-density difference between both the detectors.

52. In analyzers based on gas density, if the sample carries a gas having a higher density than the detector which of the following occurs?
a) It will cause a net downward flow
b) It will cause a net upward flow
c) It splits into two beams
d) There will be no difference in flow
Answer: It will cause a net downward flow

53. Which of the following bridges are used in analyzers based on gas density?
a) Wheatstone bridge
b) Kelvin’s bridge
c) Anderson’s bridge
d) Schering’s bridge
Answer: Wheatstone bridge.

54. 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.

55. 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.

56. 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.

57. 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.

58. 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.

59. 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.

60. 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.

61. 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.

62. 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.

63. Which of the following is not a detector used in mid Infrared Spectrophotometer?
a) Thermopile
b) Thermistor
c) Pyroelectric cell
d) Golay cell
Answer: Golay cell.

64. Which of the following is the chopping frequency used for industrial analyzers in the simple infrared analyser for gas analysis?
a) 2-10 Hz
b) 2-50 Hz
c) 2-100 Hz
d) 2-150 Hz
Answer: 2-10 Hz.

65. Why is the use of infrared analyzers limited when it comes to the analysis of inorganic compounds?
a) Slow response occurs
b) Less accurate results occur
c) Strong absorption of IR radiation by water
d) Small range
Answer: Strong absorption of IR radiation by water.

66. Which of the following is used as a source in the simple infrared analyzer for gas analysis?
a) Tungsten filament lamp
b) Nernst glower
c) Hot-wire spiral
d) Mercury arc lamp
Answer: Hot-wire spiral.

67. Which kind of filter is used in improved version of infrared gas analyzer at the output end?
a) Low pass filter
b) High pass filter
c) Narrow bandpass filter
d) Wide bandpass filter
Answer: Narrow bandpass filter.

68. Which of the following is the chopping frequency used for medical applications in simple infrared analyser for gas analysis?
a) 2-10 Hz
b) 2-50 Hz
c) 2-100 Hz
d) 2-150 Hz
Answer: 2-50 Hz.

69. Which of the following is not the drawback of conventional infrared analyzers used for gas analysis?
a) Cell is difficult to maintain
b) It is expensive to replace
c) Detector is vibration sensitive
d) Only one source is used
Answer: Only one source is used.

70. The movement of diaphragm in simple infrared analyser for gas analysis results in which of the following?
a) Variable resistance
b) Variable inductance
c) Variable capacitance
d) Variable conductance
Answer: Variable capacitance.

71. Which of the following is used as detector in improved infrared analyzer used for gas analysis?
a) PbSe
b) MgCl2
c) ZnCl
d) CuCl2
Answer: PbSe.

72. Which of the following is not the characteristics of Indium arsenide photovoltaic detector used in infrared analyzers for hydrocarbons?
a) It operates at ambient temperature
b) Has maximum detectivity at 3.4µm
c) Sensitivity increases at longer wavelength
d) It has no response to radiation of wavelength greater than 4µm
Answer: Sensitivity increases at longer wavelength.

73. In calibration of CO2 analyser, in order to establish zero calibration which of the following is used as sample?
a) Oxygen
b) Hydrogen
c) Inert gases
d) Nitrogen
Answer: Inert gases.

74. Which of the following concepts are not used in magnetic wind instruments?
a) Change in resistance due to cooling by magnetic wind
b) Displacement of membrane by magnetised oxygen
c) Difference in pressure difference between two gases having varying concentration of oxygen
d) By measuring temperature using thermometer
Answer: By measuring temperature using thermometer.

75. Which of the following does not occur in Hartman and Braun oxygen analyzer based on the magnetic wind?
a) Oxygen is attracted to the magnetic field
b) Oxygen becomes less paramagnetic due to rise in temperature
c) Resistance change in a resistance connected to the Wheatstone bridge occur
d) Wheatstone Bridge becomes balanced due to temperature change
Answer: Wheatstone Bridge becomes balanced due to temperature change.

76. Which of the following bridges are used in magnetic wind instruments?
a) Wheatstone bridge
b) Kelvin’s bridge
c) Anderson’s bridge
d) Schering’s bridge
Answer: Wheatstone bridge.

77. Magnetic wind analyzers are also known as which of the following?
a) Thermo-magnetic analyzers
b) Electro-magnetic analyzers
c) Thermo-analytical analyzers
d) Hot wire analyzers
Answer: Thermo-magnetic analyzers.

78. In OXYMAT-M oxygen analyser which of the following is usually used as reference gas?
a) Hydrogen
b) Nitrogen
c) Helium
d) Ambient air
Answer: Ambient air.

79. Which of the following is not a cause of the error that could occur in Hartman and Braun oxygen analyzer based on the magnetic wind?
a) The filament temperature could be affected by changes in thermal conductivity of the carrier gas
b) Hydrocarbons in sample stream may react on the heated filaments
c) Gravitation chimney flow effect lead to errors when cross tube is horizontal
d) Combustible gases may react on the heated filaments
Answer: Gravitation chimney flow effect lead to errors when cross tube is horizontal.

80. Which of the following is used in magnetic wind instruments to determine the amount of oxygen?
a) Change in resistance
b) Change in capacitance
c) Change in inductance
d) Change in concentration
Answer: Change in resistance.

81. How are the hydrocarbons in the samples removed in magnetic wind instruments?
a) By using a cold trap
b) By using a filter
c) By using a semipermeable membrane
d) By using magnetic effect
Answer: By using a cold trap.

82. The extremely high inertia of the thin membrane in the oxygen sensor allows it to rapidly attain equilibrium.
a) True
b) False
Answer: False

83. Hydrocarbons need to be removed from the sample gas to avoid errors in Hartman and Braun oxygen analyzer.
a) True
b) False
Answer: True.

84. Vibration excitation occurs only if the sample has hetero-atomic molecules.
a) True
b) False
Answer: True.

85. Luft detector cell which uses gas as detection mechanism is not vibration sensitive.
a) True
b) False
Answer: False.

86. 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.

87. Nitrogen dioxide can be detected with a paramagnetic analyser.
a) True
b) False
Answer: True.

88. When hot-wires are used as detectors amplification is not required.
a) True
b) False
Answer: False

89. The use of thermistor eliminates the requirement for amplification.
a) True
b) False
Answer: True.

90. Thermistors have positive temperature-coefficient of resistance.
a) True
b) False
Answer: False.

91. Changes in the composition of gas stream give rise to changes in thermal conductivity of the gas stream.
a) True
b) False
Answer: True

92. 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.

93. Polarographic cells used for measuring the partial pressure of oxygen are temperature-sensitive.
a) True
b) False
Answer: True

94. In the gold film sensor, the change in resistance is proportional to the concentration of H2S.
a) True
b) False
Answer: True.

95. The voltage required for striking the discharge in the presence of nitrogen is 1500V.
a) True
b) False
Answer: True.

96. The light output from the discharge tube is interrupted by means of a rotating slotted disc.
a) True
b) False
Answer: True

97. In Paramagnetic oxygen analyzer, when no oxygen is present the magnetic force balances torque of the fibre.
a) True
b) False
Answer: True.

Comments