Heat of Combustion Multiple Choice Questions and Answers

1. Flue gas discharge velocity through chimney of a big thermal power plant may be around __________ m/sec.

a) 0.5

b) 500

c) 10

d) 50

Answer: 10

2. 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: 10 & 3

3. Calorific value of coal middling generated in coal washeries during washing of coal may be around __________ Kcal/kg.

a) 1000

b) 4000

c) 6000

d) 8000

Answer: 4000

4. If the enthalpy change for a reaction is zero, ΔG° is equal to _____________

a) TΔS°

b) -TΔS°

c) -ΔH°

d) lnKeq

Answer: -TΔS°

5. The heat transferred when the H2O in the products is in the vapour state is called?

a) HCV

b) LCV

c) HHV

d) None of the mentioned

Answer: LCV

6. The heat transferred when the H2O in the products is in the liquid state is called?

a) HCV

b) LCV

c) LHV

d) None of the mentioned

Answer: HCV

7. HCV stands for?

a) Higher Combustion Value

b) Higher Convection Value

c) Higher Calorific Value

d) Higher Calorific Value

Answer: Higher Calorific Value

8. LCV stands for?

a) lower calorific value

b) lower Convection Value

c) lower Calorific Value

d) lower Combustion Value

Answer: lower Calorific Value

9. 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: both solid and liquid fuels

10. 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: heat loss to exhaust gases

11. 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: none of the mentioned

12. The maximum temperature achieved for given reactants is called?

a) Practical Flame Temperature

b) Critical Temperature

c) Theoretical Flame Temperature

d) None of the mentioned

Answer: Theoretical Flame Temperature

13. 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: Enthalpy of Combustion

14. 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: coal can be easily pulverised

15. 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

Answer: combustion

16. 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: keeping flue gas temperature very high

17. Maximum Theoretical Flame Temperature corresponds to _____________

a) Partial Combustion

b) Incomplete Combustion

c) Complete combustion

d) None of the mentioned

Answer: Complete combustion

18. In pure oxygen, the maximum flame temperature is _____________

a) higher than the theoretical flame temperature

b) lower than the theoretical flame temperature

c) equal to the theoretical flame temperature

d) none of the mentioned

Answer: higher than the theoretical flame temperature

19. For exothermic reactions, free energy change is?

a) positive

b) negative

c) zero

d) none of the mentioned

Answer: negative

20. Maximum permissible temperature in a gas turbine is?

a) Fixed

b) Variable

c) Linearly increasing

d) Linearly decreasing

Answer: Fixed

21. Combustion of pulverised coal as compared to that of lump coal _____________

a) develops a non-luminous flame

b) can be done with less excess air

c) develops a low temperature flame

d) provides a lower rate of heat release

Answer: can be done with less excess air

22. Spontaneity of a chemical reaction depends on?

a) Enthalpy of reaction

b) Energy of reaction

c) Gibbs Free Energy

d) None of the mentioned

Answer: Gibbs Free Energy

23. For endothermic reactions, Gibbs free energy change has to be?

a) negative

b) positive

c) zero

d) none of the mentioned

Answer: positive

24. The free energy of chemical elements at 1 atm & 25HoC is assumed to be?

a) Negative

b) Positive

c) Zero

d) None of the mentioned

Answer: Zero

25. The maximum turbine flame temperature can be can be controlled by?

a) amount of oxygen extracted

b) amount of air supplied

c) amount of air extracted

d) none of the mentioned

Answer: amount of air supplied

26. 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: less

27. Effect of dissociation is lower for lean mixtures.

a) True

b) False

Answer: True

28. Dissociation is directly proportional to temperature.

a) True

b) False

Answer: True

29. The maximum temperature achieved for given reactants is called Theoretical Flame Temperature

a) True

b) False

Answer: True

30. The heat transferred when the H2O in the products is in the vapour state is called lower Calorific Value

a) True

b) False

Answer: True

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