Relationship between free energy, enthalpy, and entropy
Enthalpy
An enthalpy change is equal to the heat that is absorbed or released when a process takes place under constant pressure. In some cases, enthalpy is referred to as "heat content"; however, "enthalpy" is an intriguing and unusual term, so we usually use it instead. Historically, the words "entropy" and "enthalpy" come from the Greek, meaning "turning" and "warming", respectively. Entropy is usually pronounced with the first syllable stressed, whereas enthalpy is usually pronounced with the second syllable stressed.H = U + PV
Enthalpy of the entire system is denoted as H
Volume = V
Pressure = P
Gibb's free energy comes from subtracting enthalpy from temperature and entropy. In other words;
G = H – TS
Where,
Entropy is S
Temperature is denoted as T
G is Gibb’s energy
H is enthalpy
- For a spontaneous process, the entropy of the universe always increases according to the second law of thermodynamics.
- Changes in entropy are determined by the G coefficient.
- During constant temperatures and pressure reactions, ΔG is meaningful only. The reaction in this system starts as well as ends at room temperature whereas it is also open into the atmosphere at constant pressure.
- An individual type of chemical change can be thermodynamically determined by ΔG as a single master variable. If the free energy of the reactants is greater than the products then the entropy of the system/world automatically increases and hence, the reaction occurs spontaneously when the free energy of the products is less than the reactants. A ΔS universe is the sum of a ΔS system and a ΔS environment
- The process occurs spontaneously if ΔG is negative and is called exergonic.
- To determine the spontaneity of the system, the temperature of the system is highly dependable.
Redox potential
Redox potential is a specific indication of the degree to which both oxidizing and reducing properties of a substance have reached equilibrium, such as a mixture of reducing and oxidizing components. The redox potential can be expressed as follows:- The chemical reactivity of substances when exposed to environmental conditions
- Various substances and systems can be predicted to exhibit corrosion protection
Redox potential is a measurement of the oxidizing-reducing ability of a system, according to the electrochemical balance. A substance's oxidation potential determines its ability to absorb oxygen, remove hydrogen, and lose electrons. An electron is attracted to hydrogen when it has a reduction potential.
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