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The second rule of thermodynamics aids in determining if a process will be spontaneous, as well as predicting whether a reaction will be spontaneous in the forward or backward direction (or whether it is at equilibrium!) using variations in Gibbs free energy.For a spontaneous process, the second rule of thermodynamics states that the entropy of the world always increases.
The change in Gibbs free energy is defined as ΔG=ΔH−TΔS
at constant temperature and pressure.
When ΔG is negative, a process is said to be exergonic since it occurs spontaneously.Temperature can affect spontaneity.
Calculating Gibbs free energy change:
Although ΔG is temperature dependent, it’s usually safe to assume that the ΔH and ΔS values are temperature independent as long as the reaction does not entail a phase shift.
That means we can utilise ΔG at any temperature if we know ΔH and ΔS. We won’t go over how to compute ΔH and ΔS in great depth, although there are a variety of ways to do it, including:
Estimating ΔHreaction using bond enthalpies
Calculating ΔH using standard heats of formation,ΔfH∘
Calculating ΔH and ΔS using tables of standard values.
We can also calculate ΔG using the standard free energy of formation, ΔfG.when the process occurs under standard conditions (all gases at 1 bar pressure, all concentrations are 1M, and T=25 degrees Celsius).
ΔG=ΔH-T × ΔS
ΔH=ΔG+T × ΔS and
ΔS=(ΔH-ΔG) / T
Free Energy:
The thermodynamic free energy is a term used in engineering and science to calculate the thermodynamics of chemical or thermal processes. The change in free energy is the maximum amount of work that a thermodynamic system can achieve in a process at constant temperature, and its sign indicates whether the operation is thermodynamically helpful or prohibited. Because it frequently contains potential energy, free energy is not absolute, and it is contingent on the choice of a zero point. As a result, physical relevance is limited to relative free energy levels or changes in free energy.
The free energy is a thermodynamic state function, just like the internal energy, enthalpy, and entropy.
Non-spontaneous reactions include:
Non-spontaneous processes are those that do not occur spontaneously. A non-spontaneous reaction is one that cannot occur without the assistance of an external source of energy. Water does not move from a lower to a higher level, and neither does heat flow from a cold to a hot body, nor do solute particles in a solution accumulate in one region, and so on.
Non-spontaneous process features include:
Process that does not occur on its own, but only as a result of the intervention of an external force or influence.e.g
Compression of gas is an example of Endothermic.Reduce entropy via increasing enthalpy.
A chemical reaction in which the typical change in free energy is positive and energy is absorbed is known as a nonspontaneous reaction. Work or heat can be used to carry out non-spontaneous processes. Water, for example, can be moved from a lower level to a higher one by people or mechanical means; heat can be transported from a refrigerator’s cold interior to the heated exterior; gases can be compressed to a smaller capacity, and so on.
Spontaneous Process:
A spontaneous process in chemistry is one that occurs without the use of external energy. Because spontaneity is unrelated to kinetics or response rate, a spontaneous process might occur swiftly or slowly.
The transformation of carbon in the form of a diamond into graphite is a classic example, which may be expressed as follows:
C(s,diamond)→C(s,graphite)
Equilibrium in Thermodynamics:
The study of thermal, electrical, chemical, and mechanical forms of energy is known as thermodynamics. The study of thermodynamics includes physics, engineering, and chemistry, among other subjects. The study of how energy varies during a chemical reaction is the most significant branch of thermodynamics for chemistry.
Consider the general equilibrium reaction below, which includes the species A, B, C, and D, as well as the stoichiometric coefficients a, b, c, and d.
aA+bB⇌cC+dD
The species on the left side of the equilibrium arrow are known as reactants, while those on the right side of the equilibrium arrow are known as products.
A reaction’s direction is determined by how low the overall free energy is. The Gibb’s free energy function calculates a reaction’s free energy at constant temperature and pressure, which is characteristic of many tabletop chemical reactions.
G=HTS, where T is the temperature in kelvin and G, H, and S are the differences in Gibbs free energy, enthalpy, and entropy between the products and reactants, respectively.
Conclusion:
The temperature of the fluid entering the heat exchanger from both sides, as well as the flow rates of those fluids, determine the amount of energy transported across it. The system is said to have experienced a cyclic process if the fluid travels through several processes and then returns to its original state. A cyclic process is studied using the first law. At steady state, the energy entering any component equals the energy leaving that component.
