Chapter 8, Problem 8.30CP

Interpretation Introduction

Interpretation:

For the given reaction the reaction corresponding to each arrow and has to be written.  The location of reactants and products have to be identified in the given Hess’s law diagram.

Concept Introduction:

• The heat content of the system is represented by ‘H’ and it is the sum of internal energy ‘E’ and product of volume and pressure,

$H=E+PV$

•  $\Delta H$ refers to change in enthalpy of the system,

$\Delta H=\Delta E+P\Delta V$

• 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,

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

• Hess’s law diagram illustrates the individual steps involved in a reaction and the enthalpy changes corresponding to it.