Question

Explain gibbs energy ?

Answer 1

In thermodynamics, the Gibbs free energy (or Gibbs energy) is a thermodynamic potential that can be used to calculate the maximum reversible work that may be performed by a thermodynamic system at a constant temperature and pressure.

Answer 2

It can be defined as follows :-

☆ Gibbs introduced a thermodynamic function which involves both enthalpy (H) and entropy (S) function this is known as gibbs energy (or) gibbs function (G).

☆ The amount of energy available from a system which can be put to useful work at constant temperature and pressure is called gibbs free energy.

☆ The difference between the enthalpy and the product of entropy & temperature is called Gibbs energy.

It is represented mathematically as $G=H-TS$

Where G = Gibbs Energy (or) Gibbs function

The change in Gibbs energy for the system

But $\Delta \: T$ for isothermal change ( T = Constant )

$\Delta \: G= \Delta \: H-T \Delta \: S$

Usually the subscript 'system' is dropped and we simply write this equation as $\Delta \: G= \Delta \: H-T \Delta \: S$

$\rm{We \: know}$

$\Delta S_{total} = \Delta S_{sys} + \Delta S_{surr}$

If the system is in thermal equilibrium with the surrounding, then the temperature of the surrounding is same as that of the system. Also increase in enthalpy of the surrounding is equal to decreasing enthalpy of the system.

$\Delta S_{surr} = \frac{- \Delta H _{sys}}{T}$

Multiplying by T, we have;

$T \: \Delta S_{total} =T \Delta S_{sys} - \Delta H_{sys}$

$- T \: \Delta S_{total} = - T \Delta S_{sys} + \Delta H_{sys}$

$\Delta G_{sys} = -T \Delta S{total}$