Question

Calculate the ΔH of the following reaction: CO2(g) + H2(g)O -> H2CO3(g) if the standard values of ΔHf are as follows: CO2(g) : -393.509 KJ/mol, H2O(g): – 241.83 KJ/mol, and H2CO3(g) : – 275.2 KJ/mol.

(a) +360.139 KJ

(b) +350.129 KJ

(c) – 360.139 KJ

(d) -350.129 KJ

I have been asked this question by my college director while I was bunking the class.

My enquiry is from Enthalpy Change Due to Reaction topic in chapter Energy Balance of Bioprocess Engineering

Answer 1

The correct choice is (a) +360.139 KJ

Easy explanation: ΔH° = ƩΔvpΔH°f (products) – ƩΔvrΔH°f (reactants) so this means that you add up the sum of the ΔH’s of the products and subtract away the ΔH of the products:

(- 275.2 KJ) – (-393.509 KJ + -241.83KJ) = (-275.2) – (-635.339) = + 360.139 KJ.