Power Plant Engineering Multiple Choice Questions on “Heat of Combustion-I”.
1. Internal energy of combustion products is ______________ than that of reactants.
a) less
b) more or less (depends on state of fuel)
c) same
d) more
Answer: a
Clarification: The internal energy of combustion is given by uRP=UP-UR which gives a negative value.
2. Higher efficiency in combustion of solid fuel cannot be achieved by ___________
a) keeping flue gas temperature very high
b) proper fuel preparation
c) supplying correct quantity of combustion air
d) adopting efficient fuel-firing technique and equipment
Answer: a
Clarification: Keeping flue gas temperature very high does not result in increased efficiency of solid fuel.
3. Bomb calorimeter is used determine the calorific value of ___________
a) solid fuels
b) liquid fuels
c) both solid and liquid fuels
d) none of the mentioned
Answer: c
Clarification: Bomb calorimeter can be used to determine the calorific value of both solid and liquid fuels.
4. Which of these is not a reason for reduction in maximum flame temperature in actuality?
a) incomplete combustion
b) heat loss to exhaust gases
c) excess air requirements
d) heat loss to surroundings
Answer: b
Clarification: Maximum flame temperature is defined on the temperature of products; hence it cannot be a reason for reduction in flame temperature.
5. Grindability index of a coal is 100. It implies that the __________
a) coal can be easily pulverised
b) coal can be pulverised with great difficulty
c) coal can’t be pulverised
d) power consumption in grinding the coal will be very high
Answer: a
Clarification: Grindability of an object is the ease with which the object can be reduced into powdered form. A measure of the same is the Grindability index of coal.
6. Tar yield in the low temperature and high temperature carbonisation of dry coal may be respectively __________ percent.
a) 10 & 3
b) 3 & 10
c) 15 & 8
d) 10 & 20
Answer: a
Clarification: Tar yield in the low temperature and high temperature carbonisation of dry coal may be respectively 10 & 3 percent.
7. High amount of sulphur and phosphorous in coke causes __________
a) decrease in its calorific value
b) increase in its strength
c) brittleness of steel made by using it
d) none of the mentioned
Answer: d
Clarification: None of the effects are caused by the increased strength of sulphur & phosphorus in coke.
8. The difference between the enthalpy of products & the enthalpy of reactants when complete combustion occurs at specific temperature & pressure is called?
a) Enthalpy of burning
b) Enthalpy of Combustion
c) Enthalpy of complete combustion
d) None of the mentioned
Answer: b
Clarification: Enthalpy of Combustion is defined as, “The difference between the enthalpy of products & the enthalpy of reactants when complete combustion occurs at specific temperature & pressure”.
9. The internal energy of products minus the internal energy of reactants for complete combustion at specific temperature & pressure gives the internal energy of?
a) combustion
b) partial combustion
c) complete combustion
d) none of the mentioned