Chapter 18, Problem 18.103SP

Interpretation Introduction

Interpretation:

The standard entropy change ${\text{(ΔS}}^{\text{°}})$, standard enthalpy change ${\text{(ΔH}}^{\text{°}})$ and standard free energy change ${\text{(ΔG}}^{\text{°}})$ in the given reaction has to be found.

Concept introduction:

Entropy is the measure of randomness in the system.   Standard entropy change in a reaction is the difference in entropy of the products and reactants.  ${\text{(ΔS}}^{\text{°}}{}_{\text{rxn}}\text{)}$  can be calculated by the following equation.

  ${\text{ΔS}}^{\text{°}}{}_{\text{rxn}}{\text{ = S}}^{\text{°}}{}_{\text{Products}}-{\text{ S}}^{\text{°}}{}_{\text{reactants}}$

Where,

  ${\text{S}}^{\text{°}}{}_{\text{reactants}}$ is the standard entropy of the reactants

  ${\text{S}}^{\text{°}}{}_{\text{Products}}$ is the standard entropy of the products

Enthalpy is the amount energy absorbed or released in a process.

The enthalpy change in a reaction ${\text{(ΔH}}^{°}{}_{\text{rxn}}\text{)}$ can be calculated by the following equation.

  ${\text{ΔH}}^{°}{}_{\text{rxn}}{\text{ = ΔH}}^{\text{°}}{}_{\text{produdcts}}{\text{- ΔH}}^{\text{°}}{}_{\text{reactants}}$

Where,

  ${\text{ΔH}}^{\text{°}}{}_{\text{reactants}}$ is the standard entropy of the reactants

  ${\text{ΔH}}^{\text{°}}{}_{\text{produdcts}}$ is the standard entropy of the products

The equation given below helps us to calculate the change in free energy ${\text{(ΔG}}^{°})$ in a system.

${\text{ΔG}}^{°}\text{ = }\Delta {{\rm H}}^{°}\text{- T}\Delta {\text{S}}^{°}$

Where,

  $\text{T}$ is the absolute value of temperature