Engineering Chemistry Multiple Choice Questions on “Combustion Calculation”.
1. Which of the following law is not used in combustion calculation?
a) The law of conservation of mass
b) The law of definite proportion
c) The law of multiple proportion
d) The law of conservation of energy
Answer: c
Clarification: According to the law of multiple proportion, “If two elements combine together to form more than one compound, than the ratios of masses of the second element which combines with a fixed mass of first element will be ratios of small whole number”. Since combustion does not involve multiple elements, this law is not required.
2. Which of the following cannot be calculated in combustion calculation?
a) Calorific value of fuel
b) Composition of fuel
c) Composition of the flue gas
d) Nature of combustion
Answer: a
Clarification: The calorific value of coal can be calculated by using bomb calorimeter. If two of the following are given from composition of fuel, composition of the flue gas and nature of combustion than the third one can be calculated in the combustion.
3. Which of the following is the ideal gas equation for 1 mol of gas?
a) PV = nRT
b) PV = 6.022nRT
c) PR = nVT
d) PV = RT
Answer: d
Clarification: The ideal gas equation is as follows-
PV = nRT, since n=1
Therefore, PV=RT.
where P is pressure, V is volume, R is gas constant, T is temperature and n is the number of moles.
The value of R is 8.314 J/mol K.
4. What is the gram molecular volume of all gases at normal temperature pressure?
a) 2.24 L
b) 22.4 L
c) 224 L
d) 2240 L
Answer: b
Clarification: According to the Avogadro law, The gram molecular volume of all gases at N.T.P. (i.e., 0 0C and 760 mm abs) is 22.4 litres. The corresponding volume in the English system is 359 cu. Ft.
5. Which of the following laws can be used for calculating the volume of gas at a given temperature and pressure?
a) Boyle’s and Avogadro law
b) Charle’s and Avogadro law
c) Charle’s and Dalton’s law
d) Boyle’s and Charle’s law
Answer: d
Clarification: Boyle’s and Charle’s law can be used for reducing the volume of a gas at a given temperature and pressure to the corresponding volume at any other specific conditions of temperature and pressure with the help of the equation-
(PV)/T = (P1V1)/T1.
6. What is the absolute temperature of gases at N.T.P.?
a) -2730C
b) 2730C
c) -273 K
d) 273 K
Answer: a
Clarification: At N.T.P. the temperature is 0 0C. Therefore at absolute condition, the temperature will be, -2730C. The temperature will be equal to 0 K.
7. Which of the following reaction is not involved in combustion calculations?
a) CH4 + 2O2 → CO2 + 2H2O
b) 2C + O2 → 2CO
c) N2 + O2 → 2NO
d) 2H2 + O2 → 2H2O
Answer: c
Clarification: Combustion means conversion of a reactant in the form of CO2 and H2O. The CO obtained in 2C + O2 → 2CO option is again oxidized to form CO2. The calculation of combustion in done by taking number of moles in consideration.
8. Analysis for combustion of solids is always done on weight basis.
a) True
b) False