Entropy Definition
Entropy is the scientific concept that is a physical property that is associated with the state of disorder, uncertainty, or randomness. It can be defined in several ways and can be applied in the various stages of cosmology, thermodynamic stage, etc. This concept was introduced by the German physicist, Rudolf Clausius in the year 1850. From the viewpoint of thermodynamics, to define entropy microscopic details of a system are not considered but it is defined in the terms of properties of thermodynamics such as pressure, temperature, heat capacity, and entropy. The statistical definition was developed at the later stage of the properties of thermodynamics and it is defined in terms of the molecular motions of a system.
Entropy is a thermodynamic function that depends on the state of the system and not on the path followed. It is represented by S in terms of standard state it is represented by S0. The SI unit of the entropy is J/K mol and the CGS unit is cal/K mol. The greater disorder is seen in the isolated system. Chemical reactions happen when the reactants break to form more products hence the entropy also increases instantaneously. If a system is at a higher temperature then the randomness increases hence the entropy order is as follows gas > liquids > solid.
Change in Entropy Formula
Entropy is the measure of disorder or randomness of a system. It depends on the initial and final state of a system thus the determination of the absolute value of entropy is difficult. Entropy change is defined as the amount of heat absorbed or emitted isothermally and it is divided by the absolute temperature.
In terms of thermodynamic definition, entropy depends on the change during physical or chemical changes and it is expressed as:
dS = \[\frac{dq_{rev}}{T}\]
The Change in Entropy Formula in Terms of the Initial and Final State is as Follows:
ΔS= Sf - Si
To measure the change in initial and final states the integrated expression of entropy formula of thermodynamics is given as:
ΔS= Sf - Si = ∫\[\frac{dq_{rev}}{T}\]
If the S value is positive then the system is said to be in spontaneous condition, if it is negative then it is non-spontaneous and if the S value is zero then the system is said to be at equilibrium condition.
The Entropy Equation in Terms of Statistical Definition is as Follows:
S = kbln Ω
Here kb represents Boltzmann constant, value is 1.3806485210-23 m2 kg s-2 K-1 Ω
denotes the number of microscopic configurations.
Molar Entropy Formula
Standard molar entropy is defined as the degree of randomness of a mole of a particular sample with respect to the standard state conditions. SI unit of molar entropy is J/mol K. If the obtained molar entropy value is positive then the entropy is in increasing conditions and if the entropy value is negative then the entropy value is decreasing. According to the second law of thermodynamics, entropy value in the case of an isolated system always increases but sometimes entropy decreases. This happens when the lab setting is made and due to the changes that occur in the outer environment of the system the change in the entropy value is determined.
The change in molar entropy value can be found by the difference in the sum of molar entropies of reactants and products. The molar entropy equation is as follows:
ΔS0 reaction = ∑ nPS0 products - ∑ nPS0 reactants
FAQs on Entropy Formula
1. For the Triple Point of Water, The Entropy Value is Constant. Why?
Ans: The simultaneous equilibrium between the solid, liquid, and gas phases is obtained in certain situations which are known as triple points. The entropy of the gas phase is greater than the liquid phase, and the entropy of the liquid phase is greater than the solid phase. At this point, the value of temperature and pressure will remain constant thus by analyzing all these aspects we can say the triple point value is constant.
2. What are the Causes for Entropy?
Ans: The amount of entropy in a system is affected by several factors: suppose if the temperature increases then the entropy value also increases and vice-versa.
If the energy input is more in the system then the molecules are excited and the amount of random activity increases.
Entropy increases by an increase in the gas molecules in the system.
3. Having Entropy in a System is Good or Bad. Explain.
Ans: For the isolated systems the entropy value will not decrease. Generally, entropy is not considered as good or bad. For some cases, the system works only when the increase in entropy value is found. This includes some of the chemical reactions, by this, we can say entropy is good for the reactions that helps to sustain our lives but there are some conditions entropy might cause damage as well.
