Chapter 18, Problem 18.25QP

Interpretation Introduction

Interpretation:

The free energy $({\text{ΔG}}^0)$ value has to be calculated given the iron hydroxide $Fe{(OH)}_2$ equilibrium reaction at $25°C$.

Concept Introduction:

Thermodynamics is the branch of science that relates heat and energy in a system.  The four laws of thermodynamics explains 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 second law of thermodynamics says that entropy of the universe is increasing.  The change in entropy in the universe is given by the summation of entropy change in the system and surroundings.

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

In thermodynamics, 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.

The equation given below helps us to calculate the change in free energy in a system.

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

Ksp (or) Kw: Equilibrium constant, the value of $\text{Kw}$ varies with temperature.  Its value is usually taken to be $\text{1}{\text{.00 x 10}}^{\text{-14}}{\text{mol}}^{\text{2}}{\text{dm}}^{\text{-6}}$ at room temperature.  In fact, this value is a bit less than 25°C.