Question

What is the heat of reaction for CH4 + 2O2 -> CO2 + 2H2O, if heat of formation of CH4, O2, CO2 and H2O are 10 J, 5 J, 6 J, and 12 J respectively?

(a) -10 J

(b) 10 J

(c) -20 J

(d) 20 J

The question was posed to me in an internship interview.

My doubt stems from Heat (Enthalpy) of Reaction in section 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

The correct choice is (b) 10 J

The explanation is: Heat of reaction = 2*12 + 6 – 2*5 – 10 = 10 J.