This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Coal – 2”.
1. At what temperature does the ash is determined by heating to complete its combustion?
a) 400o C
b) 600o C
c) 850o C
d) 750o C
Explanation: Precisely the determination of ash is done by heating it at 400o C, until most of its carbonaceous matter is burnt off. Then is it heated at 750o C for one hour so as to complete its combustion.
2. In ultimate analysis, how does the percentage of carbon and hydrogen are determined?
a) By using pure oxygen
b) By using pure nitrogen
c) By using pure sulphur
d) By using pure silicon
Explanation: The weight of sample carrying carbon and hydrogen is placed in steam of pure oxygen in a combustion reaction similar to that for the analysis of organic compounds. Carbon and hydrogen are respectively converted into CO2 and H2O which are then absorbed settled down into different chambers.
3. What is the product obtained in the determination of the percentage of nitrogen by ultimate analysis?
a) Nitrogen di-oxide
b) Nitrogen oxide
d) Ammonium ion
Explanation: The sample containing nitrogen is added to Kjeldahl flask, in which the nitrogen present is converted into the ammonium salts. The sample is then made alkaline with the help of alcoholic NaOH. Ammonia is liberated and is distilled into a measured amount of standard acid.
4. Carbon, hydrogen and oxygen directly contribute towards the calorific value of the coal.
Explanation: Carbon and oxygen contributes to the calorific value of the coal, whereas oxygen content of is generally associated with the moisture. The higher the percentages of carbon and oxygen in coal, the better is the quality of coal. The lower the oxygen content of the coal, greater is its calorific value.
5. Which of the following substance contributes towards its heating value?
Explanation: Pure sulphur contributes towards the heating effect of coal, whereas the combustion products of sulphur such as SO2 and SO3 have corrosion effects on the equipment. Nitrogen present in the coal is of negligible amount due to which it does not have effect on properties of coal.
6. Which of the following is the expression for determination of calorific value of coal using Davies formulae? (where CV is calorific value, %H is percentage of hydrogen, %C is percentage of carbon, %O is percentage of oxygen and %S is percentage of sulphur.)
a) CV = (6.543×%H + 403)[%C/3 + %H – (%O – %S)/8]
b) CV = (6.543×%H + 403)[%C/3 + %H + (%O – %S)/8]
c) CV = (6.543×%H – 403)[%C/3 + %H – (%O – %S)/8]
d) CV = (6.543×%H – 403)[%C/3 + %H + (%O – %S)/8]
Explanation: This formulae is based on ultimate analysis of fuel. The calorific value calculated here is expressed in B.Th.U./lb. Here we have only one calorific value not such as the Dulong’s formulae where we have GCV and NCV.
7. How can we calculate the calorific value of coal using proximate analysis?
a) By using Seyler’s formulae
b) By using Dulong’s formula
c) By using Davies formulae
d) By using Nakamura’s formulae
Explanation: The proximate analysis of the coal depends on moisture, ash content, volatile matter and fixed carbon. The Nakamura’s formulae is as follows-
CV = a [V – (%Ash/10)] + 140.4 C
Here a depends on the percentile of volatile matter.
8. Which region of Gondwana coals have prime coking coals deposits?
Explanation: The Gondwana region covers the areas of Chhattisgarh, West Bengal and Madhya Pradesh. The volatile matter present in these deposits of coal is about 28-32 %. It is also found in Giridh and East Bokaro.
9. Which type of coal is found in the Cutch and Lameta ghat of Narbada valley?
Explanation: These coals belong form the Jurassic period. The tertiary coal are found in the Assam, Kashmir and Rajasthan. The cretaceous coal are found in Garo hills.
10. On what basis does the grading of coals is done in India for coals containing high moisture?
a) On the basis of its calorific value
b) On the basis of its volatile matter
c) On the basis of its ignition temperature
d) On the basis of its ash content and moisture
Explanation: For coals containing low moisture content, the grading is done by the calculation of percentile of moisture whereas for high moisture content, both ash and moisture content are taken into consideration. It is not done on the basis of its calorific value.
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