Engineering Chemistry Multiple Choice Questions on “Coal – 1”.
1. What is the time required for the formation of young brown coals?
a) 107 years
b) 3×108 years
c) 3×109 years
d) 1010 years
Answer: a
Clarification: For the formation of matured coals (bituminous and anthracite) 3×108 years are required where as for the young brown coal (peat and lignite) 107 years are required. The temperature for the formation of coal is greater than 300o.
2. Which of the following substance is transformed to coal in its early stage?
a) Animal debris
b) Bacteria
c) Vegetable debris
d) Non-living compounds
Answer: c
Clarification: Vegetable debris is formed by the microbial degradation of dead plants. The bacteria act as an agent is the transformation of vegetable debris into coal and animal debris are converted into petroleum products.
3. How is peat directly converted into anthracite by the process of parallel evolution (Hilt’s law)?
a) By maintaining the acid conditions
b) By the process of consolidation and dewatering
c) By the aerobic decay of peat
d) By continuous eliminations of H2 gas
Answer: d
Clarification: When there is continuous elimination of H2 gas, it creates an anaerobic condition due to which there is loss O2 which creates anthracite directly. For aerobic decay, under sedimentary rocks lignite and bituminous coal are formed under different conditions.
4. Which of the following coal contains alternative dull and laminated layers?
a) Cannel coals
b) Banded coals
c) Splint coals
d) Bog-head coals
Answer: b
Clarification: Banded coals are bituminous coals that are identified as vitrain, clarain, durain and fusain. Splint coals are black in colour which burns freely without swelling and cannel coals consist of a greasy lustre.
5. Proximate analysis includes the estimation of ash, carbon, hydrogen, sulphur, nitrogen and oxygen.
a) True
b) False
Answer: b
Clarification: Proximate analysis is used for the determination of moisture, volatile matter, ash and fixed carbon. Ultimate analysis is used for the following given purposes.
6. Why is the high percentage of moisture undesirable for coal?
a) It increases the rate of combustion
b) It increases the cost of the coal
c) It reduces the calorific value of coal
d) It decreases its ignition temperature
Answer: c
Clarification: Moisture acts as a barrier in combustion which consequently decreases the calorific value of the coal. Moisture can be removed by drying the coal and the transportation of coal becomes easy.
7. Which of the following component is not a constituent of coal?
a) Moisture
b) Ash
c) Fixed carbon
d) Volatile matter
Answer: d
Clarification: Volatile matter consists of a complex mixture of gaseous and liquid products resulting from the thermal decomposition of the coal. Fixed carbon and ash are constituents of coal where as volatile matter is obtained after the decomposition of coal.
8. For manufacturing of metallurgical coke which of the following properties a coal should have?
a) Low volatile matter and high fixed carbon content
b) High volatile matter and high fixed carbon content
c) High volatile matter and low fixed carbon content
d) Low volatile matter and low fixed carbon content
Answer: a
Clarification: Coal having low volatile matter burn with a short flame and have a good heating value due to which it is preferred and high fixed carbon content helps to burn a coal completely. High volatile matter produces long flames and has a low heating value.
9. Ashes with fusion temperature above than 1430oC are called as ___________
a) Fixed ash
b) Free ash
c) Refractory ash
d) Fusible ash
Answer: c
Clarification: The ash which is present within the mass of coal is called as fixed ash. Fusible ash is the ash that has a fusible temperature less than 1200oC. Free ash can be removed by washing of coal.
10. At what temperature should the coal be heated so as to determine the moisture content of coal?
a) 90-100oC
b) 145-155oC
c) 125-140oC
d) 105-110oC
Answer: d
Clarification: Moisture is generally determined by heating a known quantity of air-dried coal to 105-110oC for one hour so as to get an exact value of the percentile of moisture. The loss of weight in coal determines the percentile of moisture in the coal. If the temperature is shifted from this position it will affect the percentile of oxygen.