Chapter 18, Problem 18.16QP

Interpretation Introduction

Interpretation:

The reason for considering the ${\text{ΔG }}_{\text{sys}}$ to find the spontaneity of the process over ${\text{ΔS}}_{\text{univ}}$ has to be explained and the conditions to use ${\text{ΔG }}_{\text{sys}}$.to predict the spontaneity of the process has to be found.

Concept Introduction:

Thermodynamics is the branch of science that relates heat and energy in a system.  The four laws of thermodynamics explain the fundamental quantities such as temperature, energy and randomness in a system.  Entropy is the measure of randomness in a system.  For a spontaneous process there is always a positive change in entropy. The change in entropy of the universe ${\text{(ΔS}}_{\text{univ}})$ is the sum of the change in entropy of the system ${\text{(ΔS}}_{\text{sys}})$ and surroundings ${\text{(ΔS}}_{\text{surr}})$.

${\text{ΔS}}_{\text{univ}}{\text{=ΔS}}_{\text{sys}}{\text{+ΔS}}_{\text{surr}}$

 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 G.  All spontaneous process is associated with the decrease of free energy in the system. The equation given below will enable us find the spontaneity of a reaction.  The equation given below helps us to calculate the change in free energy in a system.

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

Where,

  $\text{ΔG }$ is the change in free energy of the system.

  $\Delta {\rm H}$ is the change in enthalpy of the system.

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

  $\Delta \text{S}$ is the change in entropy in the system.