Question

What is the enthalpy change of a reaction at 30^oC, if the enthalpy of reactant at 30^oC and 25^oC are 18 J and 15 J, and enthalpy of product at 30^oC and 25^oC are 10 J and 8 J, and the enthalpy change of reaction at 25^oC is 45 J?

(a) 10 J

(b) 25 J

(c) 50 J

(d) 100 J

The question was posed to me during a job interview.

Question is taken from Heat (Enthalpy) of Reaction 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 option is (c) 50 J

The explanation is: Heat of reaction = (18 – 15) + (10 – 8) + 45 = 50 J.