# Chemical Engineering Questions and Answers – Heat of Combustion

This set of Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Heat of Combustion”.

1. What is the heat of reaction if the heat of combustion of products is 10 J and heat of combustion of reactants is 5 J?
a) -5 J
b) 5 J
c) 10 J
d) Cannot be determined

Explanation: Heat of reaction = 5 – 10 = -5 J.

2. What is the heat of reaction if the heat of combustion of products is 10 J and heat of combustion of reactants is 15 J?
a) -5 J
b) 5 J
c) 10 J
d) Cannot say

Explanation: Heat of reaction = 15 – 10 = 5 J.

3. What is the heat of reaction if the heat of combustion of products is 40 J and heat of combustion of reactants is 25 J?
a) 5 J
b) 10 J
c) 15 J
d) -15 J

Explanation: Heat of reaction = 25 – 40 = -15 J.

4. What is the heat of reaction if the heat of combustion of products is 25 J and heat of combustion of reactants is 15 J?
a) -5 J
b) 5 J
c) -10 J
d) 10 J

Explanation: Heat of reaction = 15 – 25 = -10 J.

5. What is the heat of reaction if the heat of combustion of products is 2 J and heat of combustion of reactants is 10 J?
a) 8 J
b) -8 J
c) 4 J
d) -4 J

Explanation: Heat of reaction = 10 – 2 = 8 J.
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6. What is the heating value of 10 Kg of coal with heat of combustion 10 J/Kg?
a) -10 J
b) 10 J
c) -100 J
d) 100 J

Explanation: Heating value = – Heat of combustion = -10*10 = -100 J.

7. What is the heating value of 2 Kg of coal with heat of combustion 15 J/Kg?
a) -15 J
b) 15 J
c) -30 J
d) 30 J

Explanation: Heating value = – Heat of combustion = -15*2 = -30 J.

8. What is the difference between higher heating value and lower heating value if the product has 5 moles of H2O and Enthalpy of vaporization is 10 J/mole at standard conditions?
a) 10 J
b) -10 J
c) 50 J
d) -50 J

Explanation: HHV – LHV = 5*10 = 50 J.

9. What is the difference between lower heating value and higher heating value if the product has 2 moles of H2O and Enthalpy of vaporization is 40 J/mole at standard conditions?
a) -40 J
b) 40 J
c) -80 J
d) 80 J

Explanation: LHV – HHV = -2*40 = -80 J.

10. What is the value of higher heating value if the value of lower heating value is 10 J and the product has 5 moles of H2O and Enthalpy of vaporization is 4 J/mole at standard conditions?
a) 10 J
b) 20 J
c) 30 J
d) 40 J

Explanation: HHV = 10 + 5*4 = 30 J.

11. What is the heat of reaction for CH4 + 2O2 -> CO2 + 2H2O, if the heat of combustion of H2O = 5 J, CO2 = 10 J, O2 = 0, and CH4 = 25 J?
a) -5 J
b) 5 J
c) -10 J
d) 10 J

Explanation: Heat of reaction = 25 + 0 – 10 – 2*5 = 5 J.

12. What is the heat of reaction for N2 + 3H2 -> 2NH3, if the heat of combustion of N2 = 5 J, H2 = 2 J, and NH3 = 15 J?
a) -5 J
b) 5 J
c) -19 J
d) 19 J

Explanation: Heat of reaction = 3*2 + 5 – 15*2 = -19 J.

13. What is the heat of reaction for 2CO + O2 -> 2CO2, if the heat of combustion of CO = 20 J, O2 = 5 J, and CO2 = 25 J?
a) 5 J
b) -5 J
c) 15 J
d) -15 J

Explanation: Heat of reaction = 20*2 + 5 – 2*25 = -5 J.

14. What is the heat of reaction for H2 + Cl2 -> 2HCl, if the heat of combustion of H2 = 2 J, Cl2 = 10 J, and HCl = 10 J?
a) -8 J
b) 8 J
c) -10 J
d) 10 J

Explanation: Heat of reaction = 10 + 2 – 2*10 = -8 J.

15. What is the heat of reaction for C6H6 + 3H2 -> C6H12, if the heat of combustion of H2 = 2 J, C6H6= 30 J, and C6H12 = 25 J?
a) -6 J
b) 6 J
c) -11 J
d) 11 J

Explanation: Heat of reaction = 30 + 2*3 – 25 = 11 J.

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