Engineering Questions with Answers - Multiple Choice Questions
Applied Chemistry MCQ – Analysis of Coal and Selection
In proximate analysis, which of the following elements can be found?
a) % of moisture content
b) % of carbon
c) % of hydrogen
d) % of nitrogen
Explanation: The proximate analysis is also called as quantitative analysis. It is used to find the % of moisture content, volatile matter, ash content and fixed carbon in coal.
From the raw piece, coal is manufactured by ________
a) under crushing
b) over crushing
c) perfectly crushed
Explanation: The coal is manufactured by perfectly crushing the raw piece because if the raw material is under crushed and over crushed then the chemical content varies and cannot be good for combustion.
The moisture content in the coal can be given by heating the coal for _____ hours.
Explanation: To determine the moisture content of the coal, the coal is heated at the temperature 105-1100C in a silica crucible for 1 hour later it is dried, cooled and weighed.
To find the % of volatile matter in coal, it must be heated in the crucible at ______ temperature.
Explanation: The moisture free coal is taken into a silica crucible and again it is heated at the temperature 9250C+200C for 7 minutes then it is first cooled in air and late in a dessicator.
To calculate the % of ash content the dry coal is heated in ____________
a) blast furnace
b) muffle furnace
c) reverberatory furnace
d) electric furnace
Explanation: The ash content is found by heating the moisture less coal in muffle furnace. Reverberatory furnace is a metallurgical or process furnace.
The % of the fixed carbon can be given by _________
a) %C=[loss in weight due to removal of C/weight of coal sample]*100
b) %C=[weight of coal/12*100]
c) %C=100-(% of ash)
d) %C=100-(% of moisture+% of volatile matter+% of ash)
Explanation: The % of carbon can be determined easily because the coal will have the highest amount of carbon content. So, from 100 we have to subtract the other contents % to get % of carbon.
High % of moisture is undesirable because _________
a) increases the cost of transport
b) increases the cost of calorific value
c) increases the cost of efficiency
d) decreases the cost of storage cost
Explanation: If there is more moisture content in the coal then it is difficult to transport it because the moisture will change into steam.
The moisturizing the coal before introducing into furnace is called as _________
Explanation: The process of moisturizing the coal is called tempering. Combustion means complete burning. Filtering is the process to remove unwanted contents from the substance.
Ultimate analysis of coal is also called as _________
a) quantitative analysis
b) elementary analysis
c) qualitative analysis
d) secondary analysis
Explanation: The ultimate analysis of coal is called as qualitative analysis and the proximate analysis of coal is called as quantitative analysis of coal.
In determination of % of C and H, the coal is burnt in the stream of _______
a) pure sulphur
b) pure nitrogen
c) pure alcohol
d) pure oxygen
Explanation: The carbon and hydrogen are burnt in the stream of pure oxygen so that they get converted into CO2 and H2O which are passed through Cacl2 and KOH bulbs.
% of nitrogen can be determined by the process _________
a) dulong’s formula
b) orsat’s apparatus
c) kjeldahl’s method
d) fractional distillation
Explanation: The dulong’s formula is used to find calorific value of the coal. Orsat’s apparatus is used for analysis of the flue gas. Fractional distillation is used in purification of petroleum. So, kjeldahl’s process is used for determination of nitrogen.
During metallurgical operations, n2 causes ___________
a) hardness to sample
b) softness to sample
c) moisture to sample
d) heat to sample
Explanation: During metallurgical processes, nitrogen causes hardness to the sample, but the presence of nitrogen does not affect the utility of the coal for great extent as it is present in small amounts.
Weight of the coal is 2g and after heating the coal sample, the weight of the coal is 1.82g. What is the % of the moisture in coal?
Explanation: We know that % of moisture=[(w1-w2)/weight of coal]*100, where w1=weight of the coal sample, w2=weight of the coal after heating. After substituting the given values in the formula, you’ll get 9% as an answer.
Here’s the calculation step-by-step:
((2 – 1.82) / 2) * 100
==> (0.18/2) * 100
==> 0.09 * 100
Find the % of C from the following data.
% of moisture:10g % of volatile matter:9.5g % of ash:11.6g
Explanation: We know that, % of C=100-(% of moisture+% of volatile matter+% of ash). Use the formula to get the answer 68.9g.
An increase in 1% of percentage of oxygen decreases the calorific value by ________
Explanation: The increase in 1% of oxygen results in a decrease of 1.7% of calorific value. So, always good fuel must contain less amount of oxygen.