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Introduction
If the value of Gibbs free energy is known the direction and movement of spontaneous change can be known.At constant temperature and pressure, a spontaneous change in a system goes in the direction of decreasing free energy. In general, the total entropy change is the primary criterion for determining the spontaneity of any process. We may claim there is a change in enthalpy along with the change in entropy since most chemical processes fall into the closed system and open system categories.
Entropy defines the randomness of molecules, thus entropy changes and either enhances or lowers the randomness. This randomness of molecules can affect the movement . As only the randomness of a molecule cannot define a process to be spontaneous thus, Gibbs free energy is used to know whether the process is spontaneous or not.
Gibbs free energy, also known as Gibbs function, Gibbs energy, or free enthalpy, is a term used to measure the greatest amount of work done in a thermodynamic system when temperature and pressure remain constant. The sign ‘G’ stands for Gibbs free energy. Its energy is often measured in Joules or Kilojoules. The maximum amount of work that may be extracted from a closed system is defined as Gibbs free energy. The Gibbs free energy is determined using Gibbs Helmholtz equation defined as G=TH-S. Where T is the temperature, H is the change in enthalpy, S is the change of entropy and G is the change in Gibbs free energy.
Josiah Willard Gibbs, an American scientist, discovered this trait in 1876 while performing experiments to anticipate the behaviour of systems when they are joined or whether a process can occur concurrently and spontaneously. “Available energy” was another name for Gibbs free energy. It can be thought of as the quantity of useful energy available in a thermodynamic system that can be put to work.
Spontaneity
Let’s try to grasp the concept of spontaneity. A spontaneous process is irreversible, and it can only be stopped by external forces. The degree of randomness in a system is measured by its entropy.
The Gibbs equation allows us to predict reaction spontaneity directly from enthalpy and entropy measurements. When a reaction is exothermic, the system’s enthalpy is negative, resulting in a negative Gibbs free energy. As a result, all exothermic reactions are considered spontaneous. When the enthalpy of the system is positive, endothermic reactions occur spontaneously under two conditions:
The temperature is extremely high, causing the Gibbs energy value to be negative.
To make the Gibbs free energy negative, the entropy shift must be quite high.
Spontaneity can only indicate whether or not a reaction can occur, not whether or not it will. At Standard Temperature and Pressure (STP), for example, the spontaneous conversion of diamond to graphite occurs, but it is a gradual process. The makeover will take years to complete.
Entropy
The calculation of a device’s thermal energy per unit temperature inaccessible for usable work is known as entropy. Since research is produced from organized molecular motion, the sum of entropy is also a measure of a system’s molecular disorder or randomness.
Predicting a reaction’s spontaneity
In general, the total entropy change is the most important criterion for determining the spontaneity of any process. We may claim there is a change in enthalpy along with the change in entropy since most chemical processes fall into the closed system and open system categories. Because entropy change affects molecular movements and hence enhances or lowers randomness, entropy change alone cannot account for the spontaneity of such a process. As a result, the Gibbs energy change is used to explain the spontaneity of a process. If the value of G<0, then the process is spontaneous and if G>0 then the process is non spontaneous. Gibbs’ energy is a state function with a wide range of applications.
Spontaneous Reaction
A spontaneous reaction is one in which the production of products is favoured under the conditions of the reaction. A blazing blaze is an example of a spontaneous reaction (see graphic below). A fire is exothermic, which implies that the system’s energy decreases when heat is expelled into the environment. Because the majority of a fire’s products are gases like carbon dioxide and water vapor, the system’s entropy rises throughout most combustion reactions. Combustion processes occur spontaneously due to the combination of a drop in energy and a rise in entropy.
Non-spontaneous reaction
A nonspontaneous reaction is one in which the generation of products is not favoured under the given conditions. One or both of the driving factors must prefer the reactants over the products for a reaction to be nonspontaneous. To put it another way, the reaction is endothermic, has a drop-in entropy, or both.
It’s important not to conflate the term spontaneous with the idea that a reaction happens quickly. Even though the reaction is exceedingly slow, product formation is preferred in a spontaneous reaction.
Conclusion
In thermodynamics, Gibbs free energy is referred to as a thermodynamic potential. Moreover, this potential is used to calculate the most reliable reversible work that one thermodynamic device can carry out at steady pressure and temperature. Additionally, the measuring unit of Gibbs free energy is Joules in SI.
When any response takes place at a steady pressure P and steady temperature T, the second one law of thermodynamics may be organized for Gibbs energy definition. Moreover, even as the use of Gibbs free energy to decide the spontaneity of a technique, the focus is on G. Thus, absolutely the value isn’t taken into consideration here. Hence, the value of G on this technique is the difference among its initial value and its very last value.
In chemistry, Gibbs energy alternate spontaneity of a technique is the only that doesn’t require any outside energy. Moreover, it’s far considered natural because it takes place itself, with none outdoor influence. The spontaneous method may be quick or slow as it is not related to kinetics rate.
