Introduction :
Thermodynamics : The branch of science which deals with different forms of energy & their interconversion.
Terms to be used in Thermodynamics
It means the condition in which the system is present.
It can be specified/defined by measuring/ specifying some observable/measurable properties of the
system like pressure, volume, temperature, amount of substance, elasticity, heat capacity etc
Functions or properties of the system which are dependent on mass or on size of the system are called
Extensive Properties
When there is no change in any observable or measurable property of a system with time then the
system is said to be in thermodynamic equilibrium
Types of thermodynamic process on basis of state/conditions
Types of thermodynamics processes on basis of the way the
processes are carried out
These are two ways by which a system can interact or can exchange energy with its surroundings.
Any energy given to system is taken positive so heat given to system = positive
heat given out from system / taken out from system = Negative
Law of energy conservation :
Energy of total universe is always conserved
Calculation of different quantities in First Law of
Thermodynamics (FLOT)
Law of equipartion of energy
Calculation of Heat (q)
Energy that is transmitted from one system to another in such a way that difference of temperature is not
directly involved is known as work. It is a path function
Calculation of work for different type of process on an ideal gas
(i) Single step isothermal expansion
We are assuming expansion against atmospheric pressure which need not be the case in a given problem
isothermal compression of an ideal gas
Calculation
ADIABATIC PROCESS
Operation of adiabatic process
omparison of Adiabatic Expansion (single stage Vs Infinite stage)
Comparison of Adiabatic Expansion (single stage Vs Infinite stage)
Adiabatic Irreversible process
(calculation of state parameters)
Calculation
Law of thermodynamics
Entropy Calculation
As the surrounding is an infinite heat reservoir hence, no. amount of heat given to the surrounding
can cause turbulance in it, hence all heat exhanges with surroundings are considered to be
reversible
Isothermal process
Adiabatic Process (Isoentropic process)
Isobaric process
Isochoric Process
Entropy Calculation for phase transformations
Entropy Calculation solid or liquid systems
The entropy of perfect crystals of all pure elements & compounds is zero at the absolute
zero of temperature
For chemical reaction
Gibb’s Helmholtz Equation
New criteria of spontaneity
At standared conditions
Enthalpy of a substance :
1 Every substance has a fixed value of enthalpy under any particular state. Though, its exact value cannot be
calculated but it has some finite fixed value.
2 The enthalpy of one mole of a substance called molar enthalpy in any particular state can be assigned symbol
It is not possible to determine the absolute value of the molar enthalpy of a substance. However, based on the
following convention, the relative values of standard molar enthalpies of formation of various substances can be
built
Enthalpy of Reaction from Enthalpies of Formation
Hesss Law of constant heat summation
It is the enthalpy change when one mole of a compound combines with the requisite amount of oxygen to give
products in their stable forms.
Enthalpy of combustion are usually measured by placing a known mass of the compound in a closed steel
container (known as bomb calorimeter) which is filled with oxygen at about 30 bar pressure
The integral enthalpy of solution at the given concentration is the enthalpy change when one mole of the solute
is dissolved in a definite quantity of solvent to produce a solution of a desired concentration.
Enthalpy of hydration of anhydrous or partially hydrated salts :
Enthalpy of hydration of a given anhydrous or partially hydrated salt is the enthalpy change when it combines
with the requisite amount of water to form a new hydrated stable salt
The amount of heat released when one gram equivalent of an acid is neutralised by one gram equivalent of a
base
Whenever a weak acid (or base) reacts with a strong base (or acid), the release of heat is less than
Enthalpy of transition is the enthalpy change when one mole of one allotropic form changes to another
The enthalpy change when one mole of hydrated ions is obtained from element in its standard state as.
The bond enthalpy is the average of enthalpies required to dissociate the said bond present in different gaseous
compounds into free atoms or radicals in the gaseous state. While bond dissociation enthalpy is the enthalpy
required to dissociate a given bond of some specific compound
Estimation of Enthalpy of a reaction from bond Enthalpies
Relation between energy and enthalpy of a reaction
