The Second Law of Thermodynamics in Chemistry

Introduction:

In various interpretations of the second law of thermodynamics, the idea of entropy is established as a physical attribute of a thermodynamic system.It can be used to predict if processes are forbidden while meeting the first rule of thermodynamics’ requirement for energy conservation, and it can also be used to specify the conditions that must be met for spontaneous processes. The second law can be stated as follows: when isolated systems are left to spontaneous evolution, their entropy cannot decrease because they always reach a state of thermodynamic equilibrium where the entropy is maximum at the given internal energy. The irreversibility of natural processes is explained by an increase in the combined entropy of the system and its surroundings, which is commonly referred to as the arrow of time.

2nd law of Thermodynamics:

If you’ve ever dropped a glass and watched it shatter, you know there’s no way to get the unbroken glass back. This is how irreversibility works . According to the second law of thermodynamics, heat energy cannot be transferred from a lower temperature to a higher temperature without the addition of energy. This is why running an air conditioner for an extended period of time is expensive.

2nd law of Thermodynamics equation:

The second law of thermodynamics is represented mathematically as;

ΔSuniv  >  0

where ΔSuniv is the shift in the universe’s entropy.

Entropy is a measure of energy or chaos within a closed system, as well as a measure of a system’s randomness . It can be thought of as a quantitative metric for describing energy quality. Meanwhile, there are just a few factors that cause the entropy of a closed system to increase. To begin with, heat is exchanged with the environment in a closed system while mass remains constant. The system is disrupted as a result of the change in heat content, which increases the system’s entropy. Second, intrinsic changes in the molecular movements of the system are possible. This produces disturbances, which in turn cause irreversibilities inside the system, increasing the entropy of the system .

Entropy in Thermodynamics:

Clausius established the idea of entropy as a precise manner of expressing the second rule of thermodynamics to provide a quantitative measure for the direction of spontaneous change. In an isolated system (one that does not exchange heat or work with its surroundings), spontaneous change always progresses in the direction of increasing entropy, according to the Clausius form of the second law. The ice block and the stove, for example, are two elements of an isolated system whose overall entropy grows as the ice melts .

Clausius’s Statement:

The second rule of thermodynamics’ Clausius statement asserts that “it is impossible to create a mechanism that functions in a cycle and generates no impact other than the transfer of heat from a cooler body to a hotter body.”

Kelvin-Planck Statement:

“It is impossible for any device that functions in a cycle to receive heat from a single reservoir and produce a net quantity of work,” says the Kelvin-Planck assertion.

Applications of 2nd law of Thermodynamics:

• Cycle and cyclic devices are examples of applications of the Second Law of Thermodynamics.
• It is used to create a scale of absolute thermodynamic temperatures .
• It is used to calculate the theoretical performance limit of commonly used engineering systems such as heat engines and heat pumps .

Gibbs free energy:

Gibbs free energy is the internal energy of a thermodynamic system that assists in the performance of work. At constant pressure and temperature, Gibbs free energy is the energy that is converted into the system. As a result, the following equation demonstrates it :

G = H – TS

Where G is Gibbs free energy

H is the enthalpy

T is the temperature

S is the entropy

The system releases or absorbs a substantial amount of energy per volume change as it undergoes a phase transition. As a result, as heat and temperature rise, the chaos of the molecules rises, resulting in an increase in entropy. The kinetic energy increases as the heat energy increases, breaking the intermolecular binding interactions .

Conclusion:

The second law of thermodynamics states that hot things will always cool unless they are stopped. It represents a fundamental and straightforward reality about the universe: disorder, as measured by entropy, is continually increasing. We may use the second law of thermodynamics to determine how well an energy system operates in terms of energy quality .