Thermodynamic Chemistry
Thermodynamics made up two world Thermo and dynamic (Greek word ‘thermo’ means heat and dynamics means motion).
It is the branch of science which deals with relationships between heat and dynamics. or thermodynamic is a branch of science which deals with all the changes or transfer of energy that accompany the physical and chemical process.
Chemical Thermodynamic or (Thermodynamic Chemistry) is the branch of Thermodynamic which deals with the study of the process in which chemical changes and energy involved.
The entire study of thermodynamics is based upon three generalizations laws called first law, second law, and the third law of thermodynamics. These laws have arrived merely on the basis of human experience and there is no theoretical proof for any of these laws
Basic concepts & terminology of Thermodynamic Chemistry
(1) System, surroundings and Boundary:
A specified part of the universe that is under observation and consideration for the study is called the system and the remaining part of the universe which is not considered for the study is called the surroundings.
The system and the surroundings are isolated by real or imaginary boundaries. The boundary also used to defines the limits of the given system. Both The system and the surroundings are interacted across the boundary/wall.
(2) Types of systems of Thermodynamic Chemistry
(i) Isolated system: The system which has no interaction with its surroundings is known as an isolated system. The boundary of the isolated system is sealed and insulated. Neither matter nor energy can be exchanged between systems and surroundings. A material kept in an ideal thermos flask is an illustration of an isolated system.
(ii) Closed system: The System which allows to exchange energy in the form of heat, work or radiations but not matter with its surroundings, is term as a closed system.
The boundary between this type of system and surroundings is sealed but not insulated. For instance, a liquid in contact with vapor taken in a sealed tube and pressure cooker. Here energy is transfer through the wall of the cooker but the matter remains constant.
(iii) Open system: This type of system can exchange both matter and energy with its surroundings. The boundary is neither sealed nor insulated. for example, the reaction has taken place in the open containers are an example of an open system reaction of Sodium with water in an open beaker is the example of this type of system as hydrogen escape and heat of reaction is transfer to the surrounding.
(iv) Homogeneous system: A system is defined as homogeneous when it is completely uniform throughout. A homogeneous system is consist one phase only. Examples are as pure single solid, liquid or gas, mixture of gases and a true solution.
(v) Heterogeneous system: A system is defined as heterogeneous when it is not uniform throughout, i.e., it consists of two or more phases. Examples of heterogeneous systems are ice in contact with water(H2), two or more immiscible liquids, a liquid in contact with vapor, insoluble solid in contact with a liquid, etc.
(vi) Macroscopic system: A macroscopic system is one in which there are a large number of particles ( these may be molecules, atoms, ions, etc. )
(3) Macroscopic properties of the system of Thermodynamic Chemistry
Thermodynamics covers and explains the bulk behavior((a large number of chemical species)) of matter. The properties of the system which reveals the bulk behavior of matter are called macroscopic properties.
The general examples of macroscopic properties are volume, pressure, temperature, viscosity, surface tension, density, refractive index, etc. The macroscopic properties can be further divided into two types as follows
(i) Intensive properties :
The properties said to be an intensive property if they do not depend on the quantity of matter present in the system or size of the system. Its examples are temperature, pressure, density, surface tension, specific heat, refractive index, viscosity, boiling point, melting point, volume per mole and concentration, etc.
(ii) Extensive properties :
he properties said to be an intensive property if they depend on the quantity of matter present in the system. Its examples are volume, total mass, enthalpy, internal energy, entropy, etc. Extensive properties are additive in nature.
Any extensive property if represent as per unit such as per mole or per gram converts in an intensive property.
(4) State of a system and State Variables: Thermodynamic Chemistry
Macroscopic properties that are used to determine the state of a given system are referred to as state functions or state variables or thermodynamic parameters.
The changes in the state functions depend only on the initial and final states of the system, but it is independent of the manner in which the change has been brought about. In other words, the state properties are not path dependable through which changes occur. Examples are Volume, Pressure, temperature, entropy, enthalpy, free energy, etc.
(5) Thermodynamic equilibrium in Thermodynamic Chemistry
It does not show any further tendency to change its property with time is said to be a system that attained a state of thermodynamic equilibrium.
The given below three types of equilibrium exist simultaneously in a system,
(i) Chemical Equilibrium: A system in which the composition of the system remains fixed and definite.
(ii) Mechanical Equilibrium: In Mechanical equilibrium, No chemical work is done between different compartments of the system itself or between the system and surrounding. It can be achieved by the remaining pressure constant throughout the process.
(iii) Thermal Equilibrium: A equilibrium where the temperature of the system remains constant i.e. no flow of heat between the system and its surrounding.
(6) Thermodynamic processes :
When the thermodynamic system goes through changes from one state to another, the operation is termed a process. The various types of the processes are
(i) Isothermal process: In this process, the temperature remains constant temperature means dT = 0. In this process heat exchange b/w system and surrounding take place and the system is not thermodynamically isolated. during the isothermal process, the internal energy of the system remains constant (dE=0). This because dT=0 thus dE=0
(ii) Adiabatic process: In this process, no exchange of heat takes place between the system and surroundings. The system is thermally isolated, i.e., Q = 0, and its boundaries are insulated.
Note: In this adiabatic process change in heat dQ =o but Temperature of the system varies (dT ≠ 0)
(iii) Isobaric process: In this process, the pressure remains constant throughout the process i.e., dP = 0.
(iv) Isochoric process: In this process volume remains constant throughout the process, dV = 0.
(v) Cyclic process: When a system undergoes a number of different processes and finally returns to its initial state is known as a cyclic process. For a cyclic process-the internal energy and enthalpy remains constant that means dE= 0 and dH = 0.
(vi) Reversible process: A process that takes place infinitesimally slowly, i.e. here opposing force is infinitesimally smaller than driving force of the process and when infinitesimal increase by a small amount in the opposing force can reverse the process, it is said to be a reversible process.
(vii) Irreversible process: When the process takes place from the initial state to the final state in a single step infinite time and cannot be reversed, it is termed as an irreversible process. Amount of entropy increases in the irreversible process. Irreversible processes are spontaneous in nature. All-natural processes are irreversible in nature
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Reversible Process
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Irreversible Process
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It is an ideal process and takes place infinite time
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It is a spontaneous process and takes place infinite time
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The driving force is infinitesimally larger than that of opposing force.
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The driving force is much greater than the opposing force.
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It is in equilibrium at all stages of the process
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Equilibrium exists only at the initial and final stages.
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Work done is maximum
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Work done is not maximum
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It is difficult to realize and performed in practice
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It can be performed in practice
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