Chapter 18.5, Problem 2RC

Interpretation Introduction

Interpretation: the value of ${\Delta }_r{S}^{\circ }$ for the given reaction is to be identified from the given options.

Concept introduction:

In Spontaneous process, energy transfer from higher concentration to lower, or the energy is dispersed.

Entropy (S) is the quantity to measure the dispersal of energy in the spontaneous processes.

The equation for finding $\Delta S^{\circ }(system)$ is,

${\Delta }_r{S}^{\circ }=\sum n{S}^{\circ }(products)-\sum n{S}^{\circ }(reac\text{tants)}$

${\Delta }_r{H}^{\circ }(system)$ is the change in enthalpy is calculated by sum of the product of stoichiometric coefficients and molar enthalpies of products minus sum of the product of stoichiometric coefficients and molar enthalpies of reactants. That is,

${\Delta }_r{H}^{\circ }(system)=\sum n{\Delta }_f{H}^{\circ }(products)-\sum n{\Delta }_f{H}^{\circ }(reac\text{tants)}$

Equation for $\Delta S^{\circ }(surrounding)$ is,

$\Delta S^{\circ }(surrounding)=-{\Delta }_f{H}^{\circ }(system)/T$

Equation for $\Delta S^{\circ }(universe)$,

$\Delta S^{\circ }(universe)=\Delta S^{\circ }(system)+\Delta S^{\circ }(surrounding)$