Chapter 8, Problem 8.122CHP

Interpretation Introduction

Interpretation:

$\Delta H°$ for the conversion of methane to ethylene has to be calculated using Hess’s law.

Concept Introduction:

Hess’s law is applied to calculate the enthalpy changes in a reaction.  According to Hess’s law –

“The overall enthalpy change of a reaction is equal to the sum of the enthalpy changes involving in each and every individual steps in the reaction.”

Thus if a reaction involves ‘n’ steps then enthalpy change $\Delta H°$ of the reaction is,

$\Delta H°=\Delta {\text{H}}_1^{°}+\Delta {\text{H}}_2^{°}+\Delta {\text{H}}_3^{°}\mathrm{....}+\Delta {\text{H}}_n^{°}$