# Power Plant Questions and Answers – Heat of Combustion-III

This set of Power Plant Quiz focuses on “Heat of Combustion-III”.

1. 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

Explanation: Initially, for a certain time. the change in the values of free energy change remains same and equal to zero.

2. Effect of dissociation is lower for lean mixtures.
a) True
b) False

Explanation: Effect of dissociation is directly proportional to the amount of oxygen present in the reaction.

3. 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

Explanation: Turbine maximum flame temperature is controlled entirely by the amount of air supplied.

4. If the enthalpy change for a reaction is zero, ΔG° is equal to _____________
a) TΔS°
b) -TΔS°
c) -ΔH°
d) lnKeq

Explanation: Gibbs free energy is the parameter which determines the spontaneity of the reaction after determining its randomness.

5. 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

Explanation: Flue gas discharge velocity through chimney of a big thermal power plant may be around 10 m/sec.

6. 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

Explanation: Calorific value of coal middling generated in coal washeries during washing of coal may be around 4000 Kcal/kg.

7. 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

Explanation: The amount of air required for combustion of pulverised coal is less in comparison to the amount of air in the combustion of Lump Coal.

8. For endothermic reactions, Gibbs free energy change has to be?
a) negative
b) positive
c) zero
d) none of the mentioned

Explanation: Gibbs free energy is the parameter which determines the spontaneity of the reaction after determining its randomness. For endothermic reactions, this energy difference has to be positive.

Sanfoundry Global Education & Learning Series – Power Plant Engineering.