Chapter 13, Problem 57E

Interpretation Introduction

Interpretation:

$\text{ΔrG°}$ should be calculated and compare the result with Appendix D.

Concept introduction:

The Gibb’s equation of thermodynamic purposed a relation between $\text{ΔS}$, $\text{ΔH}$ and $\text{ΔG}$ with temperature.

The mathematical expression of Gibb’s equation can be written as:

$\begin{array}{l}\text{ΔrG° = ΔrH° - TΔrS° }\\ \text{ΔrG° = ΔrG°(product) - ΔrG°(reactant)}\end{array}$

With the help of this equation one can predict the change in $\text{ΔS}$, $\text{ΔH}$ and $\text{ΔG}$.

${\text{K}}_{\text{p}}$ or $\text{Kc}$ are the equilibrium constants for the reaction which are ratio of gaseous and aqueous products to the reactant molecules.

$\text{A + B }\leftrightarrow \text{C + D }$

$\begin{array}{l}\text{K = Kp = }\frac{\text{[PC] [PD]}}{\text{[PA] [PB]}}\\ \text{K = Kc = }\frac{\text{[aC] [aD]}}{\text{[aA] [aB]}}\end{array}$

Here ‘a’ represents the active mass and ‘P’ represents the partial pressure. The relation between equilibrium constant and $\Delta \text{rG}°$ can be written as:

$\text{ΔrG° = - RT ln K}$

Here:

• R = 8.314 J / mol .K
• T = temperature in Kelvin