Answer to Question #228355 in Molecular Physics | Thermodynamics for Raghav

Question

Why gibbs energy is free ?State its importance?(100words)

Answer 1

Answer: Enthalpy and entropy factors, reflecting two opposite tendencies, cannot be an exhaustive criterion of spontaneous processes. For isobaric-isothermal processes, they are united by a function called the Gibbs energy (ΔG)

and is equal to:

ΔG = ΔH − T⋅ΔS

Gibbs energy is measured in [kJ / mol].

Equation can be written as:

ΔН = ΔG + T⋅ΔS

It can be seen from that the enthalpy of a chemical reaction contains two parts. The first term of the equation (ΔG) is equal to the maximum work Armax that can be performed by the system at equilibrium process under isobaric-isothermal conditions, ie

Gibbs energy is part of the energy effect of a chemical reaction that can be turned into work:

−ΔG = Amaxp

−ΔG = Awmax

A minus sign indicates that the system is able to perform work on the environment only by reducing the Gibbs energy due to the reaction. Because Gibbs energy can be converted into work, it is sometimes called free energy.

The second term of the right-hand side of equation - the entropy factor - is the part of the energy effect that cannot be converted into work. This part is dissipated into the environment in the form of heat, so the entropy factor TΔS called bound energy.

The Gibbs energy ΔG is a criterion for the spontaneous flow of a chemical reaction, so the sign before the numerical valueΔG

("+" Or "-") allows us to conclude about the fundamental possibility or impossibility of spontaneous reaction.

The decrease in the Gibbs energy (ΔG <0) indicates that the spontaneous course of the reaction in the forward direction under these conditions is in principle possible.

The increase in the Gibbs energy (ΔG> 0) is a condition for the impossibility of spontaneous direct reaction under these conditions.

If the Gibbs energy does not change (ΔG = 0), then the spontaneous course of the reaction is possible both in the forward and in the opposite direction, ie the system is in equilibrium.