This set of Engineering Chemistry Questions and Answers for Entrance exams focuses on “Particle Size Measurement”.
1. Which of the following is a method of particle size measurement?
a) Sieve analysis
b) Microscopic examination
c) Sedimentation analysis
d) All of the mentioned
View Answer
Explanation: Sieve analysis, microscopic examination and sedimentation analysis are the three methods of particle size measurement.
2. The minimum size of particle which can be separated through sieve analysis is ____________
a) 75 microns
b) 100 microns
c) 44 microns
d) 20 microns
View Answer
Explanation: The minimum size of particle which can be separated through sieve analysis is 44 microns. The results of sieve analysis are used to describe the properties of the aggregate and to see if it is appropriate for various civil engineering purposes such as selecting the appropriate aggregate for concrete mixes and asphalt mixes as well as sizing of water production well screens.
3. The instrument used for the examination of particle size ≥ 0.5 micron is ____________
a) Microscope
b) Electron microscope
c) Telescope
d) All of the mentioned
View Answer
Explanation: The instrument used for the examination of particle size ≥ 0.5 micron is a microscope. Microscope is an optical instrument used for viewing very small objects.
4. Sedimentation techniques are particularly useful for the particle size ranging from ____________
a) 50-10 µm
b) 40-2 µm
c) 100-50 µm
d) 80-40µm
View Answer
Explanation: Sedimentation techniques are particularly useful for the particle size ranging from 40-2 µm.
5. Sedimentation analysis is generally applicable to liquid dispersions containing _______________ % solids.
a) 5-10
b) 1-3
c) 2-5
d) 4-8
View Answer
Explanation: Sedimentation analysis is generally applicable to liquid dispersions containing 2-5% solids. It is particularly useful for the particle size ranging from 40-2 µm.
6. Select the incorrect statement from the following option.
a) In the Coulter counter, a narrow orifice is immersed in an electrolyte
b) The resistance across the orifice is continuously noted on an oscilloscope
c) The pulses occurring on the oscilloscope are counted electronically
d) The magnitude of the pulse is inversely proportional to the volume of the electrolyte displaced
View Answer
Explanation: The magnitude of the pulse is directly proportional to the volume of the electrolyte displaced and therefore to the volume of the particle. All the other options are correct.
7. The current generated in photoelectric cell represents the measure of the ____________
a) Turbidity
b) Adhesivity
c) Cohesivity
d) Viscosity
View Answer
Explanation: The current generated in photoelectric cell represents the measure of the turbidity of the suspension. Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye. It is the capacity of water to disperse the light.
8. Adsorption method for measurement of total surface area involves the evaluation of quantity of ____________
a) Helium gas
b) Oxygen gas
c) Nitrogen gas
d) Argon gas
View Answer
Explanation: Adsorption method for measurement of total surface area involves the evaluation of quantity of nitrogen gas.
9. In photo-extinction method, a source of light is directed through a suspension of ____________
a) Kerosene in cement
b) Cement in kerosene
c) Cement in water
d) Water in cement
View Answer
Explanation: In photo-extinction method, a source of light is directed through a suspension of cement in kerosene on to a photoelectric cell.
10. Fibrous fillers have a high capacity for absorbing energy because of their ____________
a) Shape
b) Size
c) Composition
d) Surface area
View Answer
Explanation: Fibrous fillers have a high capacity for absorbing energy because of their shape. As a result, they impart excellent impart strength to the material.
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