Chapter 18, Problem 18.109SP

Interpretation Introduction

Interpretation:

Value of free energy for standard state $\Delta G°$ for following reaction is to be calculated. Whether following reaction is spontaneous in forward direction or in backward direction should be determined.

$\text{U}\left(s\right)+3{\text{F}}_2\left(g\right)\to {\text{UF}}_6\left(s\right)$

Concept introduction:

The standard free-energy change use to define the free-energy change for formation of products in standard state form the reactant in standard state. It is denoted by $\Delta G°$. But when reactant and product are not present in their standard-state pressure and concentrations then the free energy change is calculated by the expression as follows:

$\Delta G=\Delta G°+RT\ln \text{Q}$

Where,

• $\Delta G$ is free energy change under nonstandard state conditions.
• $\Delta G°$ is free energy change under standard state conditions.
• $R$ is gas constant.
• $T$ is temperature.
• $Q$ is reaction quotient.

When $Q<1$, then term $RT\ln Q$ also become less than 0. This results in $\Delta G<\Delta G°$.

When $Q=1$, then term $RT\ln Q$ become equal to 0. This results in $\Delta G=\Delta G°$.

When $Q>1$, then term $RT\ln Q$ also become greater than 0. This results in $\Delta G>\Delta G°$.