Alternative Approach - The Clausis Inequality
|Introduction||What is this thing called Thermodynamics??? | Definitions | Thermal Equilibrium and Zeroth Law | Limitations|
|First Law||Work, Heat, Energy, and the First Law | Work, Heat, Energy, and the First Law (simplied) | Derivatives | Derivatives Exercise | Reversibility, Enthalpy, and Heat Capacity|
|Second Law||Things to Think About | Observations and Second Law of Thermodynamics | Alternative Approach - the Clausis Inequality | Consequences of the Second Law | Consequences of the Second Law (simplified) | Carnot Principle - motivation and examples | Equivalence of Second Law Statements*|
|Third Law||Third Law of Thermodynamics | Consequences of Third Law*|
|Development of Thermodynamics||The Thermodynamic Network | Network Exercise | Equations of State | Thermochemistry|
* Optional Section
The above development of the second law is based on intuition. It is a good approach to understanding the law, but it does not allow us to make any calculations.
Second Law Postulate
The postulate has four parts:
- There exists an extensive, additive property called ENTROPY.
- The entropy can be divided into two parts:
- The internal part is zero for reversible changes and positive for irreversible changes
- The external part (dSe) is related to heat by
- where T is always positive
The entropy is therefore the sum of the internal and external parts: [math]dS=dS_e+dS_i[/math] where dSe is given above and since dSi is either zero or positive according to the number 3 in the postulate.
This is called the CLAUSIS INEQUALITY.
The Clausis inequality is the probably the most important equation in thermodynamics.
- A postulate is a statement which is regarded as true
- Adapted from Reid, Charles E. (1990) "Chemical Thermodynamics" Singapore:McGraw-Hill