Basic Concept of Thermodynamics

Introduction

It is important to note that thermodynamics is concerned only with energy changes accompanying a given process (physical or chemical) and not with the total energy of the body. Further chemical thermodynamics is that branch of thermodynamics which deals only with chemical changes in chemical substances.

The study of thermodynamics is based on three generalizations, called the first, second and third law of thermodynamics. All these laws are based on human experience and although there is no formal proof for these laws, nothing contrary to these laws has been found so far and nothing contrary is expected.

Applications in Chemistry

1. Most of the important laws of physical chemistry such as Raoult’s law of lowering of vapour pressures, van’t Hoff law of dilute solutions, distribution law, phase rule, law of chemical equilibrium, law of thermo-chemistry and expressions for elevation in boiling point and depression in freezing point can be deduced from the laws of thermodynamics.

2. Thermodynamics helps us in predicting the feasibility of a particular process (physical or chemical), i.e. whether the process can occur or not under a given set of conditions of temperature, pressure and concentration.

3. Thermodynamics also helps in determining the extent to which a reaction would proceed before attainment of equilibrium and thus it may predict the yields of products.

Applications in Physics

The concepts of thermodynamics are applied in studying the phenomena involving light, heat or electric and magnetic fields.

Applications in Engineering

Thermodynamics helps in predicting the maximum efficiency of various types of heat engines and the maximum work obtainable from a given fuel, i.e. in the problems of combustion and power.

Limitations of Thermodynamics

1. The laws of thermodynamics are applicable only to matter in bulk, i.e. assemblage of large number of molecules (macroscopic systems), and not to individual molecules of atoms. Thus thermodynamics is independent of atomic and molecular structure of matter, i.e. it ignores the internal structure of atoms and molecules.

2. Although thermodynamics predicts about the feasibility, direction and extent of a given process under a given set of conditions, it does not tell anything about the rate at which a given process may proceed, i.e. it provides no information regarding the time taken to reach equilibrium.

3. It concerns itself only with the initial and final states of a system and gives no information about the path taken (mechanism) by a process.