Question

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

I had been asked this question in a job interview.

Query is from Standard Heat (Enthalpy) of Formation in division 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

Correct option is (b) -7 J

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