Enthalpy Vs Entropy : How Entropy And Enthalpy Are Different To Each Other

Enthalpy (H) of a thermodynamic system is an energy-like state function property that is equal to the total internal energy (U) and pressure-volume (PV) work whereas entropy is an intrinsic disorderness of a system under certain conditions. 

In thermodynamics, the change in enthalpy and entropy can be measured rather than their absolute values.

In other words, enthalpy is an amount of energy contained in a compound whereas entropy is a measure of disorderness within the compound.

History???

In 1909, a Dutch scientist named Heike Kamerlingh Onnes coined the term "Enthalpy.". Total heat content is what the word enthalpy denotes. We can determine the amount of heat added to or removed from the system using enthalpy. It is used to measure the heat of a reaction.

The term entropy was introduced by the scientist Rudolf Clausius in 1850. The concept of entropy develops from the fact that for energy to be converted to work, some dissipations must occur. This lost energy is called the "Entropy".

In this article, we're interested in learning more about the difference between "Enthalpy & Entropy" on different basis. Generally, the opposite of enthalpy is entropy. Enthalpy is the total heat content of a system whereas entropy is a measure of the amount of disorder in the system. Let us see how enthalpy differs from entropy.

Comparison Between Enthalpy And Entropy

The main difference between enthalpy and entropy is that enthalpy is the measurement of the total energy of a system which is the sum of internal energy and product of pressure and volume. On the other hand, entropy is the amount of thermal energy in a system that cannot be converted into work.

Let us look at the difference between enthalpy and entropy on a different basis;

Definition

(Enthalpy): It is a thermodynamic quantity equivalent to total heat content of a system.

(Entropy): It is the measurement of the disorderness of a system.

Symbol

(Enthalpy): It is represented by "H"  

(Entropy): It is represented by "S". 

Explanation

(Enthalpy): It is the sum of internal energy and product of PV work.

(Entropy): It is the amount of heat transferred reversibly in and out of the system at a given temperature.

Formula 

Enthalpy; H = U+PV

Entropy; dS = d/T

Unit

(Enthalpy): The SI unit of enthalpy is the same as that of energy hence can be measured in J. 

(Entropy): Its unit is Joules/Kelvin.mole.

Nomenclature

(Enthalpy): This term was given by scientist Heike Kamerlingh Onnes.

(Entropy): This term was given by scientist Rudolf Clausius.

Relation To Thermodynamics Law

(Enthalpy): It is related to the first law of thermodynamics. According to the 1st law of thermodynamics, the energy of the universe is constant.

(Entropy): It is related to the second law of thermodynamics. According to the 2nd law of thermodynamics, the entropy of the universe is always increasing.

Favor By Systems 

(Enthalpy): The natural systems always favors the minimum enthalpy.

(Entropy): The natural systems favors maximum entropy.

Responses

(Enthalpy): Change in enthalpy is positive for endothermic processes and negative for exothermic processes.

(Entropy): Change in entropy is positive for spontaneous processes and negative for non-spontaneous processes.

Reactions

(Enthalpy): It can use to measure the change in energy of the system after the reaction.

(Entropy): It can use to measure the degree of randomness of the system after the reaction.

Nature

(Enthalpy): It is a kind of energy.

(Entropy): It is the property of the matter.

Similarities Between Enthalpy And Entropy 

There are some similarities between enthalpy and entropy as well which are such that, both enthalpy and entropy are

1) State functions

2) Extensive properties

Thus, both enthalpy and entropy are zero for a cyclic process and they both are dependent on the mass/size of a substance.

FAQs

Are Enthalpy And Entropy Related?

Enthalpy and entropy are related. Enthalpy is the amount of energy released or absorbed in a system whereas, entropy is the measure of disorderness in a system. Entropy is a change in enthalpy per unit temperature. Gibb’s free energy provides the relationship between enthalpy and entropy.

➩ [ ΔG = ΔH – TΔS ]

Gibb’s free energy is equal to the change in enthalpy minus the product of temperature and change in entropy of the system.

1. If the Gibbs free energy change is positive, the reaction is non-spontaneous.
2. If the Gibbs free energy change is negative, the reaction is spontaneous.
3. If the Gibbs free energy change is zero, the reaction is at equilibrium.

Does Entropy Increase When Enthalpy Increases?

Change in enthalpy also affects entropy. For an endothermic reaction, heat is absorbed from the surroundings, so, the entropy of the surroundings decreases. For exothermic reactions, heat is released to the surroundings, so, the entropy of the surroundings increases.

Which Is More Important Enthalpy Or Entropy?

Entropy is more important than enthalpy because when the temperature changes, a significant change is observed in entropy than enthalpy.

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