Engineering Chemistry Multiple Choice Questions on “Characteristics of Coal”.
1. How does the texture of coal changes with its maturity?
a) Becomes hard, less brittle and moderately tough
b) Becomes hard, more brittle and more tough
c) Becomes hard, more brittle and less tough
d) No change
Answer: b
Clarification: The texture of coal tends to the layer present on the coal and its maturity is from lignite to anthracite. The number of layers from lignite to anthracite increases due to which the compactness increase, thus increasing its toughness, hardness and brittleness.
2. On what factors does the specific gravity of coal depends?
a) Its calorific value and ash content
b) Its ignition temperature and calorific value
c) Type of coal and ash content
d) Type of coal and calorific value
Answer: c
Clarification: Specific gravity is the ratio of the density/mass of a substance to the density/mass of reference substance. The total ash content represents its mass and
The type of coal is required for its density.
3. Which of the coal have the best heating values in terms of volatile matter?
a) Containing 20% volatile matter
b) Containing 60% volatile matter
c) Containing 30% volatile matter
d) Containing 50% volatile matter
Answer: a
Clarification: Coals containing high volatile matter produces long and smoky flame due to which its heating value decreases. Semi-bituminous coal has the highest heating value due to less volatiles content.
4. Which type of coals have the highest grindability index?
a) Steam coals
b) Gas coals
c) House coals
d) Pulverised coals
Answer: d
Clarification: Grindability is the ease with which a coal can be grounded. The grindability index of pulverised coal is about 100. This is because of the volatile matter present in the coal, the higher the volatile matter of coal, the more will be its grindability index.
5. How does the friability of the coal is tested?
a) Drop shatter test
b) Thermal cracking
c) Knocking
d) Proximate analysis
Answer: a
Clarification: Friability is the tendency of the coal to break into pieces. The more the friability, the less will be the quality of coal. Splint and cannel coal are less friable. Knocking is the unusual sound produced by an engine.
6. Which property of coal is tested in Audibert Arnu test?
a) Bulk density
b) Colour
c) Caking and coking
d) Texture
Answer: c
Clarification: This method uses a dilatometer to find out the swelling properties of coal. Caking is the ability to form a coherent cake when the coal is carbonised. If there is residue formed during carbonisation, then the coals formed are called coking coals.
7. On which property of coal does the design of bunkers for the storage of coal depends?
a) Specific gravity
b) Bulk density
c) Grindability
d) Friability
Answer: b
Clarification: Bunkers/coal bins are the containers in which the coal can be transported. Bulk density is weight of soil present in coal. According to the bulk density the design of containers are generated.
8. Which type of coals are non-caking in nature?
a) Steam coals
b) Gas coals
c) House coals
d) Pulverised coals
Answer: a
Clarification: Steam coals are volatile lignitous coals which are used in steam raising. These coals produce long smoky flames. Gas coals are strongly caking in nature.
9. Phosphorous and sulphur content in the coal tend to make a metal brittle.
a) True
b) False
Answer: a
Clarification: A coal should not contain high phosphorous and sulphur content because coal have a role in number of metallurgical operation due to which it affects the properties of metal and makes it brittle.
10. Which of the following is not a characteristic of coal?
a) Weathering
b) Slaking index
c) Moisture content
d) Bulk density
Answer: c
Clarification: Moisture content represents the total vapours present inside the coal. Moisture develops from the outside atmospheric conditions due to which it is not a characteristic of coal.