Question

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

The question was posed to me in a national level competition.

This interesting question is from Heat of Combustion topic in chapter Application of Energy Balances in the Absence of Chemical Reactions and Energy Balances: How to Account for Chemical Reaction of Basic Chemical Engineering

Answer 1

Right answer is (c) -80 J

The explanation is: LHV – HHV = -2*40 = -80 J.