13 THERMODYNAMIC EQUILIBRIUM 1.Mechanical Equilibrium 2.Thermal Equilibrium 3.Chemical Equilibrium QUASISTATIC PROCESS In which the deviation from thermodynamic equilibrium is infinitesimal and all the states through which the system passes during a quasistatic process can be considered as equilibrium states.
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THERMODYNAMIC EQUILIBRIUM
1.Mechanical Equilibrium
2.Thermal Equilibrium
3.Chemical Equilibrium
QUASISTATIC PROCESS
In which the deviation from thermodynamic
equilibrium is infinitesimal and all the states
through which the system passes during a
quasistatic process can be considered as
equilibrium states.
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Internal Energy and Temperature
“internal energy” : the energy content of a system.
1. kinetic energy of molecules (due to vibrational,
rotational or electronic energy)
2. Potential energy due to intermolecular forces ,
depends upon separation .
3. the energy of electrons and nucleiThe relationship between energy and temperature (for monatomic ideal gas)
2B
1 3av K E /m o lecu le m v k T
2 2= =
Internal Energy U = number of molecules av KE/molecule
= N (3/2) kBT
= (3/2) n RT = (3/2) P V (ideal gas)Internal energy can change by thermodynamic process
====== ZERO’th LAW of Thermodynamics =====
If two systems A and B are separately in thermal equilibrium with a third system C, then A and B are in thermal equilibrium with each other.
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• The work done is the area under the curve in a PV diagram.
• The work done depends on the path by which the system goes from the initial to the final state.
• The work done depends on the initial, final and intermediate states of the system.
Work : A path dependent function
V
P
1 2
3
V1 V2
P1
P3
Area = (V2-V1)x(P1-P3)/2
What is the total work done by system when going from state 1 to state 2 to state 3 and back to state 1 ?