Chapter 17, Problem 17.82QP

Interpretation Introduction

Interpretation:

Standard free energy ($\Delta G°$) values has to be calculated for the given $(C{u}_{2}S)$ heating reaction.

Concept Introduction:

Free energy$({\text{ΔG}}^0)$: In thermodynamics free energy or Gibbs free energy is the energy that is used to express the total energy content of a system.  According to second law of thermodynamics, in all spontaneous process is associated with the decrease in free energy of the system.  That is the change in free energy will be negative.

Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter $\text{G}$.  All spontaneous process is associated with the decrease of free energy in the system.  The standard free energy change ${\text{(ΔG}}^{\text{°}}{}_{\text{rxn}})$ is the difference in free energy of the reactants and products in their standard state.

${\text{ΔG}}^{\text{°}}{}_{\text{rxn}}\text{=}\sum {\text{nΔG}}_{\text{f}}{}^{\text{°}}\text{(Products)-}\sum {\text{nΔG}}_{\text{f}}{}^{\text{°}}\text{(Reactants)}$

Decomposition reaction: The reaction breaking down compounds (such as carbonates, nitrates or hydroxides) by heating them is called thermal decomposition.

For example,

$CaC{O}_{3(s)}\underset{}{\to }Ca{O}_{(s)}+C{O}_2{}_{(g)}$