Chapter 18, Problem 97QP

Interpretation Introduction

Interpretation:

The value of $\Delta G$ for the given reaction is to be calculated.

Concept introduction:

The sign of standard free energy change gives the direction of spontaneity of the reaction. If the free energy change is negative $\left(\Delta G^{\circ }<0\right)$, the reaction is spontaneous. It means that the formation of product is favored. On the other hand, if the free energy change is positive $\left(\Delta G^{\circ }>0\right)$, the reaction is not spontaneous. In such cases, the formation of reactant is favored. It is given by the following expression:

$\Delta G=\Delta G^{\circ }+RT\ln Q$

At equilibrium,

$\Delta G^{\circ }=-RT\ln K$

Here, $R$ is the ideal gas constant, $K$ is the equilibrium constant, and $T$ is the temperature.

There are three cases in which the reaction varies at equilibrium, according to $Q\&K.$

If $Q=K,$ then the change in free energy $\left(\Delta G\right)$ is zero. This means that the formation of neither, the reactants nor products is favored.

If $Q<K,$ then the free energy change $\left(\Delta G\right)$ is negative. This means that the formation of the products is favored over the reactants.

If $Q>K,$ then the free energy change $\left(\Delta G\right)$ is positive. This means that the formation of the reactants is favored over products.