Chapter 10, Problem 42A

Interpretation Introduction

Interpretation: Driving force needs to be defined.

Concept Introduction:

In chemistry, the driving force of a chemical reaction or "reaction force" is "chemical coupling" or Affinity A, which is measured by a negative change in free energy (Gibbs free energy -ΔG or Helmholtz free energy -ΔH) from reactants to products.

Explanation of Solution

A chemical additive can be considered the driving force of a chemical reaction.

For chemical reactive systems at constant T and P, Gibbs requires a minimum of free energy; Subsequently, G can be used to tell if the reaction continues or not.

If value of Gibbs free energy is more than 0 or positive, the reaction goes in backward direction and it cannot takes place.

If the value of G is less than 0, reaction is spontaneous and takes place in forward direction.

Also,

Enthalpy, H is the drive towards stability.

If change in enthalpy is less than 0, products are more stable than reactants (and vice versa).

Now, entropy, S is the drive towards the disorder. The products are more disordered than reactants when entropy is more than 0.

The Gibbs free energy is related to change in enthalpy and entropy as follows:

ΔG = ΔH − TΔS

From the above equation, reaction is only possible if value of change in Gibbs free energy is negative thus, for positive value of change in enthalpy, the product of temperature and change in entropy should have a larger value than change in enthalpy.