Chapter 16, Problem 16.29CP

Interpretation Introduction

Interpretation:

The sign of $\Delta H°,\Delta S°$ for the forward reaction $A\stackrel{}{\to }B$ has to be ascertained given that $\Delta H°,\Delta S°$ are assumed to be independent of temperature.

Figure 1

Concept Introduction:

• Entropy refers to measurement of randomness or disorderliness in the system.  More the number of molecules in a system more will be the movement of molecules and greater will be the entropy given that weak intermolecular forces prevails between molecules.
• Entropy is denoted by ‘S’ and $\Delta S°$ refers to change in entropy of the system.  $\Delta S°$ value positive for a phenomenon indicates the process is spontaneous.  $\Delta S°$ value negative for a phenomenon indicates the process is non–spontaneous
• The term free energy G, refers to energy available in the system to do work and enthalpy H, refers to heat content of the system.  Change in standard free energy is $\Delta G°$ and change in standard enthalpy is $\Delta H°.$
• All these three parameters are related by an equation,

$\Delta G°=\Delta H°-T\Delta S°$

• Standard free energy change $\Delta G°$ and equilibrium constant of a reaction ‘K’ are related as,

$\Delta G°=-\text{ RT ln K}$

Where,

$\begin{array}{l}\Delta G°=\text{ standard free energy change}\\ R=\text{ Universal gas constant}\\ \text{T}=\text{ Temperature}\\ \text{K}\text{= equilibrium constant}\end{array}$