Question

The calorific value of all organic compounds has the sign corresponding to a ________

(a) Exothermic reaction

(b) Endothermic reaction

(c) Single displacement reaction

(d) Synthesis reaction

This question was posed to me in examination.

This question is from Calorific Value of Fuels topic in division Steam Power Plant of Energy Engineering

Answer 1

Correct option is (a) Exothermic reaction

To elaborate: The calorific value of all organic compounds has the sign corresponding to an exothermic reaction. Because the double bond in molecular oxygen is much weaker than other double bonds or pairs of single bonds, particularly those in combustion products carbon dioxide and water, conversion of the weak bonds in o2 to the stronger bonds in CO2 and H2O releases energy as heat.