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Multiple choice question for engineering

Set 1

1. Gas-solid chromatography is based on which of the following processes?
a) Partition of the analyte between a gaseous mobile phase and a stationary liquid phase
b) Adsorption of gaseous substances on solid surface
c) Ion exchange
d) Large molecules cannot penetrate through the gel

View Answer

Answer: b [Reason:] Gas-solid chromatography is based on the adsorption of gaseous substances on a solid surface. It is useful for the separation of rare gases.

2. Which of the following components cannot be retained by gas-liquid columns but can be separated by using gas-solid chromatography?
a) Formaldehyde
b) Hydrogen sulphide
c) Benzene
d) Carbon dioxide

View Answer

Answer: b [Reason:] Hydrogen sulphide cannot be retained by gas-liquid columns. It can be separated using gas-solid chromatography.

3. Which of the following is not an advantage of gas-solid chromatography?
a) Increased column life
b) Can be used for separation of rare gases
c) Leads to semi-permanent retention of analyte
d) Ability to retain some components that cannot be easily retained by other gas chromatography method

View Answer

Answer: c [Reason:] Gas-solid chromatography leads to semi-permanent retention of analyte. Hence, it is used for limited applications.

4. The distribution coefficients of Gas-solid chromatography are greater than that of Gas-liquid chromatography.
a) True
b) False

View Answer

Answer: a [Reason:] The distribution coefficients of Gas-solid chromatography are greater than that of Gas-liquid chromatography. The stationary phase is a solid particle.

5. Which of the following columns can be used in Gas-solid chromatography?
a) Open tubular column
b) Analytical column
c) Separation column
d) Guard column

View Answer

Answer: a [Reason:] Open tubular column can be used in Gas-solid chromatography. Analytical/separation column and guard column is used in liquid chromatography.

6. Which of the following is not an advantage for the conversion of packed columns into wide bore capillaries?
a) Longer retention times
b) Longer life
c) Higher efficiency
d) Greater inertness

View Answer

Answer: a [Reason:] Wide bore capillary has shorter retention time. It is an advantage. It is undesirable to have longer retention time.

7. Which of the following is not a disadvantage of gas-solid chromatography?
a) Strong retention of polar solutes
b) Lifetime is short
c) Occurrence of catalytic changes
d) Cannot be used for very wide range of components

View Answer

Answer: b [Reason:] The lifetime of gas-solid chromatography is long. It can be used for geometrical isomers.

8. Gas-solid chromatography can be used only for separation of certain low molecular weight gaseous species.
a) True
b) False

View Answer

Answer: a [Reason:] Gas-solid chromatography can be used only for separation of certain low molecular weight gaseous species. This is because in gas-solid chromatography, semi-permanent retention of analyte only takes place.

9. Which of the following is a special adsorbent used in gas-solid chromatography?
a) Molecular sieves
b) Silica gel
c) Alumina
d) Starch

View Answer

Answer: a [Reason:] Molecular sieves are a special adsorbent used in gas-solid chromatography. It is used in open tubular columns.

10. Which of the following properties of molecular sieves make it ideal for exclusion mechanism of separation?
a) High thermal stability
b) Large inner surface area
c) Variable framework charge
d) Ability to distinguish materials on the basis of their size

View Answer

Answer: d [Reason:] Molecular sieves have the ability to distinguish materials on the basis of their size. This property can be used in separating molecules of linear structure from bulky ones.

Set 2

1. 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

View Answer

Answer: d [Reason:] Electrochemical cells are affected by interference from background gases. Some of them are sulphur dioxide, carbon monoxide, nitric oxide and chlorine.

2. 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

View Answer

Answer: b [Reason:] Solid state sensors are mainly used in combustible gas detection equipment. It is a semiconductor sensor.

3. 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

View Answer

Answer: d [Reason:] Solid state sensors are affected by interference from background gases. Some of them are hydrogen, isopropanol and ethyl and methyl mercaptan.

4. 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

View Answer

Answer: b [Reason:] Hydrogen Sulphide reacts with Lead Acetate to form Lead Sulphide which is brown in colour. Hydrogen acetate in other words is acetic acid and is colourless.

5. 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

View Answer

Answer: c [Reason:] Chemiluminescence method cannot be used for detection of hydrogen sulphide. Others method that are used are using photometric analyser and using gold film sensor.

6. 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

View Answer

Answer: a [Reason:] In solid state sensor, when heated to 150o to 300o resistance decreases with increase in H2S concentration. The decrease in resistance is a logarithmic function of H2S concentration.

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

View Answer

Answer: a [Reason:] Gold film sensor works on the principle of absorption. The change in resistance is proportional to concentration of H2S.

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

View Answer

Answer: c [Reason:] In Electrochemical cells, an oxidation-reduction reaction occurs in the presence of hydrogen sulphide. A current starts flowing and it is proportional to the concentration of hydrogen sulphide.

9. 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

View Answer

Answer: d [Reason:] For measuring H2S, the sensor must be maintained at a particular temperature. This is done by using heater. The temperature is monitored using thermistor.

10. The diagram of Electrochemical cell used for the detection of hydrogen sulphide is given below. Identify the unmarked component.
analytical-instrumentation-questions-answers-h2s-analyser-q10
a) Filter
b) Gas permeable membrane
c) Elastic layer
d) Electrolyte

View Answer

Answer: b [Reason:] The unmarked component is gas permeable membrane. Electrochemical cell is an electrochemical gas diffusion sensor.

Set 3

1. Which of the following is not true about High pressure liquid chromatography (HPLC)?
a) It requires high pressure for the separation of the specious
b) There is no need to vaporise the samples
c) It is performed in columns
d) It has high sensitivity

View Answer

Answer: b [Reason:] In High pressure liquid chromatography (HPLC), samples need to be vaporised. It has high sensitivity.

2. High pressure liquid chromatography can be performed only in columns.
a) True
b) False

View Answer

Answer: a [Reason:] High pressure liquid chromatography can be performed only in columns. This is because application of high pressure in open bed will not be effective.

3. Which of the following is not an advantage of Syringe type pumps used in High pressure liquid chromatography?
a) Independent of viscosity
b) Pulse-less flow
c) High pressure capability
d) Unlimited solvent capacity

View Answer

Answer: d [Reason:] The limitation of Syringe type pump is that it has limited solvent capacity and is inconvenient when solvents are to be changed.

4. Which of the following is not true about solvent programming which is done in high performance liquid chromatography?
a) It provides unequal bandwidths
b) It provides fast overall separation
c) It provides maximum resolution
d) It provides maximum sensitivity

View Answer

Answer: a [Reason:] Solvent programming is done to provide equal bandwidths. It provides maximum sensitivity for every solute in the sample.

5. Which of the following pulse damper takes up some amount of the pulsation energy which is released to provide smooth pressure without pulsations?
a) Flexible bellows or compressible gas passed through tee columns
b) Flexible inert diaphragm
c) Electronic pulse damper
d) Electrical pulse damper

View Answer

Answer: a [Reason:] Flexible bellows or compressible gas passed through tee columns take up some of the pulsation energy which is released to provide smooth pressure without pulsations. Its main purpose is to avoid pulses.

6. Which of the following is not a characteristic of the syringe pump used in high pressure liquid chromatography?
a) Pressure capability is high
b) Maintenance is frequent
c) Limited reservoir capability
d) Slight change of flow rate when extremely high pressure compresses the solvent

View Answer

Answer: b [Reason:] In syringe pumps, maintenance is infrequent. However, it has high pressure capability.

7. Syringe pumps used in High pressure liquid chromatography are most suitable for which of the following columns?
a) Capillary columns
b) Guard columns
c) Short-fast columns
d) Small bore columns

View Answer

Answer: d [Reason:] Syringe pumps used in High pressure liquid chromatography are most suitable for small bore columns. It is the most commonly used piston type pump.

8. Gravity feed method for solvent delivery is not used with narrow bore columns packed with fine mesh particles.
a) True
b) False

View Answer

Answer: a [Reason:] Gravity feed method for solvent delivery is not used with narrow bore columns packed with fine mesh particles. This is because they cannot deliver solvent at high pressure.

9. Which of the following cannot be done to reduce ripple in High pressure liquid chromatography?
a) Using bellows
b) Using restrictors
c) Using long nylon tube between pump and column
d) Avoiding the use of solvent pump

View Answer

Answer: d [Reason:] Solvent pumps have to be used to reduce pulses in solvent flow. When there is a pulsed flow, the efficiency of column decreases.

10. Which of the following is not true about Hydraulic capacitance flow control system used in HPLC?
a) It can be used only for liquids with low viscosity
b) It is irrespective of solvent compressibility
c) It maintains constant flow
d) It smoothens high pressure pump pulsations

View Answer

Answer: a [Reason:] Hydraulic capacitance flow control system used in HPLC is irrespective of the solvent viscosity. It is also irrespective of the solvent compressibility.

Set 4

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

View Answer

Answer: d [Reason:] Golay cell is not used in mid Infrared Spectrophotometer. It is used in far infrared spectrometer.

2. 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

View Answer

Answer: c [Reason:] The use of infrared analyzers is limited when it comes to the analysis of inorganic compounds because of the strong absorption of IR radiation by water. It is particularly used for organic compounds.

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

View Answer

Answer: a [Reason:] The chopping frequency used for industrial analysers in simple infrared analyzer for gas analysis is 2-10 Hz. The chopper is motor driven.

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

View Answer

Answer: c [Reason:] Hot-wire spiral is used as a source in simple infrared analyzer for gas analysis. Two sources are used.

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

View Answer

Answer: a [Reason:] Vibration excitation occurs only if the sample has hetero-atomic molecules. Hence, infrared analyzers are not used for gases whose molecules are formed by two identical atoms.

6. 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

View Answer

Answer: b [Reason:] The chopping frequency used for medical applications in simple infrared analyser for gas analysis is 2-50 Hz. The chopper is motor driven.

7. 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

View Answer

Answer: c [Reason:] The movement of diaphragm in simple infrared analyser for gas analysis results in variable capacitance. The diaphragm forms one plate of the capacitor.

8. 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

View Answer

Answer: d [Reason:] Two sources are used in conventional infrared analyzers used for gas analysis. To overcome the drawbacks an improved model was created.

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

View Answer

Answer: a [Reason:] PbSe is used as detector in improved infrared analyzer used for gas analysis. It is a solid state detector.

10. 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

View Answer

Answer: c [Reason:] In calibration of CO2 analyser, in order to establish zero calibration inert gases are used as sample. Generally, room air is also used.

11. 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

View Answer

Answer: c [Reason:] The sensitivity of Indium arsenide photovoltaic detector decreases at longer wavelength. It is insensitive to radiation having wavelength greater than 4µm.

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

View Answer

Answer: b [Reason:] Luft detector cell which uses gas as detection mechanism is vibration sensitive. It is also subject to cross-talk with other gases.

13. 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

View Answer

Answer: c [Reason:] The filter is used in improved version of infrared gas analyzer at the output end is narrow bandpass filter. The bandpass characteristics are matched with the absorption spectra of the gas of interest.

Set 5

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

View Answer

Answer: b [Reason:] High pressure mercury arc lamp is used as the source for Far IR Spectrophotometer. Rest of the options are used as source in Mid Infrared Spectrophotometer.

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

View Answer

Answer: c [Reason:] The wave number of near infrared spectrometer ranges between 12500 – 4000. Wavenumber is the reciprocal of wavelength.

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

View Answer

Answer: a [Reason:] Wavelength of near IR is 0.8 – 2.5 mm and for mid IR it is 2.5 – 50 mm. The wavelength of far IR is 50 – 1000 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

View Answer

Answer: b [Reason:] Oxides of Barium is not present in Nernst glower. They are constructed by fusing oxides of Zirconium, yitrium and thorium.

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

View Answer

Answer: a [Reason:] Globar is a silicon carbide rod. It is 5mm in diameter and 50mm long.

6. Bolometer, a type of detector, is also known as:
a) Resistance temperature detector (RTD)
b) Thermistor
c) Thermocouple
d) Golay cell

View Answer

Answer: b [Reason:] Bolometers are also known as thermistors. It is a type of resistance thermometer constructed of metals such as platinum or nickel.

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

View Answer

Answer: d [Reason:] Four techniques are generally used to prepare solid samples. They are: Solids run in solution, Mull technique, Solid films and pressed pellet techniques.

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

View Answer

Answer: d [Reason:] Pyroelectric materials are deutrated triglycine sulphate, triglycine sulphate and some polymers. They give rise to a potential when subjected to a heating or cooling effect.

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 increase in temperature and vice versa
c) Temperature difference gives rise to a potential difference in the material
d) Decrease in resistance due to increase in temperature

View Answer

Answer: a [Reason:] It is also known as pneumatic detector. The gases expand on heating and this in turn leads to the movement of a diaphragm just like in pneumatic sensors.

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

View Answer

Answer: b [Reason:] The mentioned technique is Mull technique. This method is used for qualitative analysis but not quantitative analysis.