# Chemical Engineering Questions and Answers – Standard Heat (Enthalpy) of Formation

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

1. For exothermic reactions, what is the heat of reaction?
a) Positive
b) Negative
c) Zero
d) Cannot Say

Explanation: In exothermic reactions, heat leaves the system, so the heat of reaction is negative.

2. For endothermic reactions, what is the heat of reaction?
a) Positive
b) Negative
c) Zero
d) Cannot Say

Explanation: In endothermic reactions, heat comes into the system, so the heat of reaction is positive.

3. Enthalpy of reactants is 15 J/Kg and enthalpy of products is 40 J/Kg, what is the heat of reaction?
a) -10 J/Kg
b) 10 J/Kg
c) -25 J/Kg
d) 25 J/Kg

Explanation: Heat of reaction = 40 – 15 = 25 J/Kg.
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4. Enthalpy of reactants is 50 J/Kg and enthalpy of products is 25 J/Kg, what is the heat of reaction?
a) -10 J/Kg
b) 10 J/Kg
c) -25 J/Kg
d) 25 J/Kg

Explanation: Heat of reaction = 25 – 50 = -25 J/Kg.

5. Enthalpy of reactants is 30 J/Kg and enthalpy of products is 10 J/Kg, what is the heat of reaction?
a) -20 J/Kg
b) 20 J/Kg
c) -10 J/Kg
d) 10 J/Kg

Explanation: Heat of reaction = 10 – 30 = -20 J/Kg.
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6. Heat of formations of A, B, C, and D, are 5 J, 10 J, 15 J, and 20 J respectively, what is the heat of reaction A + 4B -> 3C + D?
a) 10 J
b) 20 J
c) 35 J
d) 45 J

Explanation: Heat of reaction = 20 + 3*15 – 4*10 – 5 = 20 J.

7. Heat of formations of A, B, C, and D, are 5 J, 8 J, 2 J, and 15 J respectively, what is the heat of reaction 3A + B -> 3C + 2D?
a) 9 J
b) 10 J
c) 13 J
d) 15 J

Explanation: Heat of reaction = 2*15 + 3*2 – 8 – 3*5 = 13 J.

8. Heat of formations of A, B, C, and D, are 1 J, 2 J, 3 J, and 4 J respectively, what is the heat of reaction 3A + 4B -> 2C + D?
a) -1 J
b) 1 J
c) 3 J
d) 6 J

Explanation: Heat of reaction = 4 + 2*3 – 4*2 – 3*1 = -1 J.

9. Heat of formations of A, B, C, and D, are 2 J, 5 J, 3 J, and 10 J respectively, what is the heat of reaction 4A + 5B -> 2C + 2D?
a) -10 J
b) -7 J
c) -5 J
d) 0

Explanation: Heat of reaction = 2*10 + 2*3 – 5*5 – 4*2 = -7 J.

10. Heat of formations of A, B, C, and D, are 3 J, 5 J, 4 J, and 8 J respectively, what is the heat of reaction 2A + 2B -> 2C + D?
a) -5 J
b) 0
c) 5 J
d) 8 J

Explanation: Heat of reaction = 8 + 2*4 – 2*5 – 2*3 = 0.

11. In the reaction C + O2 -> CO2, if the heat liberated is 10 J, what is the heat of formation of CO2?
a) -10 J
b) 10 J
c) 0
d) Cannot be determined

Explanation: Heat of formation = -10 J.

12. In the reaction 2H2 + O2 -> 2H2O, if the heat liberated is 50 J, what is the heat of formation of H2O?
a) -25 J
b) 25 J
c) -50 J
d) 50 J

Explanation: Heat of formation = -50/2 = -25 J.

13. In the reaction 2N -> N2, if the heat liberated is 6 J, what is the heat of formation of N2?
a) – 6 J
b) 6 J
c) 0
d) Cannot be determined

Explanation: Heat of formation = -6 J.

14. In the reaction 2C + O2-> 2CO, if the heat liberated is 10 J, what is the heat of formation of CO?
a) -5 J
b) 5 J
c) -10 J
d) 10 J

Explanation: Heat of formation = -10/2 = -5 J.

15. In the reaction C + 2H2 -> CH4, if the heat liberated is -5 J, what is the heat of formation of CH4?
a) -5J
b) 5 J
c) 0 J
d) Cannot be determined

Explanation: Heat of formation = – (-5) = 5 J.

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