Revision Notes
Class - 11 Chemistry
Chapter 5 - Chemical Thermodynamics
Thermodynamics:
The study of flow of mass, heat and energy is the study of thermodynamics.
Thermodynamics terminology:
● System:
A notable part of the universe which is kept under observation is known as
the system.
● Surrounding:
The remaining part of the universe except the system which isn’t kept
under observation is known as surroundings.
In general, it can be stated as;
Universe = System + Surrounding
● Types of system:
a) Open system –
The system where flow of both, mass and heat energy take place.
Example: Human body.
b) Closed system –
The system where flow of heat energy takes place but has constant mass.
Example: Pressure cooker.
c) Isolated system –
The system where none of the flow takes place.
Example: Thermos flask.
State of system:
The state of the system can be defined and changed with respect to the changes
in state variables i.e., P, V, T and n. These variables define the conditions of the
system and change in any one of them, will change the state of the system.
Properties of system:
● Intensive properties –
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, Properties depending upon concentration and independent of mass or total
number of particles in the system. They are pressure, refractive index,
density, etc.
● Extensive properties –
Properties depending upon mass or total number of particles in the system.
They are volume, total energy, etc.
State and path function:
● State function –
The function which will be independent of the path followed but will
depend upon the initial and final states while bringing up the changes in
the system.
Example: internal energy, enthalpy, etc.
● Path function –
The function which will depend upon the path followed while bringing up
the changes in the system.
Example: work, heat, etc.
Thermodynamic equilibrium:
The system remains in equilibrium when the state variables do not change and
the below three types of equilibrium are satisfied.
● Mechanical equilibrium –
The absence of mechanical motion, constant pressure and volume brings
up the mechanical equilibrium.
● Thermal equilibrium –
The constant heat and temperature with respect to the time brings up
thermal equilibrium.
● Chemical equilibrium –
The rate of forward reaction equal to the rate of backward reaction brings
up the chemical equilibrium.
Internal energy:
The sum total of the components of the energy influenced by the internal factors
of the system is known as internal energy; often denoted by U or E.
Class XI Chemistry www.vedantu.com 2
Class - 11 Chemistry
Chapter 5 - Chemical Thermodynamics
Thermodynamics:
The study of flow of mass, heat and energy is the study of thermodynamics.
Thermodynamics terminology:
● System:
A notable part of the universe which is kept under observation is known as
the system.
● Surrounding:
The remaining part of the universe except the system which isn’t kept
under observation is known as surroundings.
In general, it can be stated as;
Universe = System + Surrounding
● Types of system:
a) Open system –
The system where flow of both, mass and heat energy take place.
Example: Human body.
b) Closed system –
The system where flow of heat energy takes place but has constant mass.
Example: Pressure cooker.
c) Isolated system –
The system where none of the flow takes place.
Example: Thermos flask.
State of system:
The state of the system can be defined and changed with respect to the changes
in state variables i.e., P, V, T and n. These variables define the conditions of the
system and change in any one of them, will change the state of the system.
Properties of system:
● Intensive properties –
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, Properties depending upon concentration and independent of mass or total
number of particles in the system. They are pressure, refractive index,
density, etc.
● Extensive properties –
Properties depending upon mass or total number of particles in the system.
They are volume, total energy, etc.
State and path function:
● State function –
The function which will be independent of the path followed but will
depend upon the initial and final states while bringing up the changes in
the system.
Example: internal energy, enthalpy, etc.
● Path function –
The function which will depend upon the path followed while bringing up
the changes in the system.
Example: work, heat, etc.
Thermodynamic equilibrium:
The system remains in equilibrium when the state variables do not change and
the below three types of equilibrium are satisfied.
● Mechanical equilibrium –
The absence of mechanical motion, constant pressure and volume brings
up the mechanical equilibrium.
● Thermal equilibrium –
The constant heat and temperature with respect to the time brings up
thermal equilibrium.
● Chemical equilibrium –
The rate of forward reaction equal to the rate of backward reaction brings
up the chemical equilibrium.
Internal energy:
The sum total of the components of the energy influenced by the internal factors
of the system is known as internal energy; often denoted by U or E.
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