Spontaneous Process: What is it and How it Works

The first law of thermodynamics includes a provision for spontaneity. Students can gain an understanding of the fact connected with a fixed energy level in an isolated system by reading this section of the textbook.

This can be demonstrated by establishing a relationship between work done on or by the system and its direction of heat flow . In thermodynamics, this is known as spontaneity.

It is not difficult to comprehend spontaneous meaning in chemistry. Many natural phenomena have a single, linear path of heat transfer across their structures. Heat flow routes are not restricted in any way by these devices.

In What Way Does a Spontaneous Reaction Differ From Other Reactions?

Reactions that occur spontaneously are represented by the equation of spontaneity.

With the change in the total entropy of a reaction, we may forecast the spontaneity of the reaction in a chemical sense. In the context of any process, this is characterized as its spontaneity. This category encompasses nearly all sorts of chemical reactions.

According to scientists, a decrease or an increase in the unpredictability of chemical reactions is facilitated by a decrease in enthalpy. Molecular movements are also influenced by them. The reason for this is that entropy changes can only occur as a result of chance. There are a slew of more processes that are waiting to be included.

By studying Gibb’s energy, students can obtain a thorough understanding of Spontaneity Chemistry as well as spontaneous equations.

Equation of Spontaneous Reaction

To explain spontaneous reactions in chemical composition, Gibb’s equation may be the most effective tool available. It is a function with a state variable. In addition, Gibb’s equation has a wide range of applications in science and engineering. Gibb’s equation depicts the change in energy at a constant temperature.

To put it another way, it can be said

ΔGsys = ΔHsys – TΔSsys

Here, 

• Change in Gibbs energy of the system equals to ΔGsys 
• Change in enthalpy of the system equals to ΔHsys 
• Change in Entropy of the system equals to ΔSsys 
• Constant Temperature of the system equals to T 

Another point to note is that when we engage in a spontaneous process, the total change in entropy is always greater than zero.

In the preceding spontaneous reaction meaning expression, the mathematical expression is as follows:

ΔSsys + ΔSsurr = ΔStotal

Here,

• ΔStotal equals total change in entropy for the process
• ΔSsurr equals to change in entropy of the surrounding
• ΔSsys equals to change in entropy of the system

The Spontaneity of A Process

The Gibbs equation allows us to predict the spontaneity of a reaction on the basis of the enthalpy and entropy values in a simple and straightforward manner. Because exothermic reactions produce negative enthalpy in the system, Gibbs free energy is negative when the reaction occurs. This leads us to conclude that all exothermic reactions occur spontaneously.

When the enthalpy of the system is positive, as in the case of endothermic reactions, the process is spontaneous under the following two conditions:

The temperature is extremely high, resulting in a negative Gibbs energy value.

The entropy change is extremely high, resulting in a negative Gibbs free energy.

Spontaneity can only indicate whether or not a reaction can take place, not whether or not a reaction will take place. For example, the conversion of diamond to graphite occurs spontaneously at Standard Temperature and Pressure (STP), although it is a sluggish process because of the high temperature and pressure required. It will take years before the transition can be fully realized.

Gibbs Energy

The Gibbs free energy is the relevant quantity for the energetics of processes for systems at constant temperature and pressure. The Gibbs free energy has a very useful property: under constant temperature and pressure, it decreases for a spontaneous process. Under such circumstances, a drop in Gibbs free energy reflects the maximum amount of energy available for work, whereas an increase in Gibbs free energy represents the smallest amount of effort required.

At constant temperature and pressure, a system’s shift from one state to another is spontaneous if the Gibbs free energy decreases. The two states are in equilibrium if the Gibbs free energy is not affected by the transformation. In other words, the Gibbs free energy of the system must be at its lowest value for the system to be in thermodynamic equilibrium at constant temperature and pressure. Because of its resemblance to the potential energy of a mechanical system, which similarly has a minimum value under equilibrium conditions, the Gibbs free energy is frequently referred to as the thermodynamic potential under constant pressure.

Conclusion

If we see any energy change in Gibbs energy of the system that is less than zero in a spontaneous chemical reaction, we can conclude that the reaction is not spontaneous. Otherwise, the reaction is not spontaneous.

From this, it may be argued that the same relationship holds true for an unpredicted response.

Exothermic reactions have a negative enthalpy, which means that the system’s energy is being used up. As a result, all exothermic reactions become spontaneous as a result of this phenomenon.

Endothermic reactions have Gibbs’ free energy turn negative, which is why they are called “negative free energy.” Only under specific circumstances, such as when the temperature rises or when the change in entropy is extremely large, does it occur.