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MHT-CET : Chemistry Entrance Exam

MHT - CET : Chemistry - Chemical Thermodynamics and Energetics Page 1

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1.

Thermodynamics:

 

The study of interconversion of heat and other forms of energy is called thermodynamics.

 

2.

System:

 

 

A specific portion of the universe which is under thermodynamic study is called a system.

 

3.

Surroundings:

 

 

The portion of the universe other than that selected for the purpose of thermodynamic study is called the surroundings.

 

4.

Types Of Thermodynamic Systems:

 

 

  1. Open System:
    A system that can exchange matter as well as energy with its surroundings is called an open system.
  2. Closed System:
    A system that can exchange only energy but not matter with its surroundings is called a closed system.
  3. Isolated System:
    A system that can exchange neither energy nor matter with its surroundings is called an isolated system

 

5.

Homogeneous And Heterogeneous Systems:

 

 

  1. Homogeneous System:
    A system, which consists of only one phase and which is uniform throughout, is called a homogeneous system.
  2. Heterogeneous System:
    A system, which consists of two or more phases and which is not uniform throughout, is called a heterogeneous system.

 

6.

Properties Of Thermodynamics System:

 

 

  1. Intensive Properties:
    The properties, which do not depend on the total quantity of matter present in the system, are called intensive properties. Example: Temperature, pressure, density.
  2. Extensive Properties:
    The properties, which depend on the total quantity of matter present in the system, are called extensive properties. Example: Amount of heat, volume, weight.

 

7.

Thermodynamic Equilibrium:

 

 

A system is said to be in thermodynamic equilibrium, if its macroscopic (measurable) properties such as temperature, pressure and composition do not undergo any change with time.

 

8.

Process:

 

 

The path by which the system changes from one state to another is called process.

 

a.

Difference Between Isothermal And Adiabatic Process

 

Isothermal Process

Adiabatic Process

1.

In an isothermal process, temperature of the system remains constant.

In an adiabatic process, temperature of the system changes.

2.

In this process, the system exchanges heat with the surroundings.

In this process, the system does not exchange heat with the surroundings.

3.

Total internal energy of the system remains constant (DE = 0).

Total internal energy DE of the system changes.

4.

Total heat content of the system changes (DH 0).

Total heat content of the system remains constant (DH = 0).

5.

In this process, the system is not thermally isolated.

In this process, the system is thermally isolated.

6.

This process can be made reversible.

This process cannot be made reversible.

7.

In this process, Q = W as DE = 0.

In this process, W = (-) DE as DQ = 0

  1. Isobaric Process:
    The process which takes place at a constant pressure is called an isobaric process.
  2. Isochoric Process:
    The process which takes place at a constant volume is called an isochoric process.
  3. Cyclic Process:
    The process involving a series of operations which finally bring the system back to its original state is called a cyclic process.

 

b.

Difference Between Reversible And Irreversible Process:

 

 

 

Reversible Process

Irreversible Process

1.

The process whose direction can be reversed at any stage by an infinitesimal increase in the opposing force is called a reversible process.

The process whose direction cannot be reversed by an infinitesimal increase in the opposing force is called an irreversible process.

2.

Such a process is not spontaneous, takes place infinitesimally slowly and takes infinite time for completion.

Such a process is spontaneous and takes finite time for completion.

3.

In this process, the thermodynamic equilibrium is always maintained between the system and the surroundings.

The thermodynamic equilibrium is attained only when the process is completed.

4.

The opposing force is infinitesimally less than the driving force.

The opposing force is significantly smaller than the driving force.

5.

It is an ideal or hypothetical process.

It is a practical or real force.

6.

Maximum work can be derived from such a process.

Work derived from such a process is always less than maximum work.

 

9.

Expression for the work obtained in an isothermal and irreversible process (against constant pressure):

 

 

W = P(V2 - V1) = PDV

  1. Work Done in Vacuum:
    As P = 0, W = 0
    i.e. when a gas expands in vacuum, no work is done.
  2. Work Done in a Cyclic Process:
    As DV = 0, W = 0
    i.e. work done in a cyclic process is always zero.

 

10.

Expression for maximum work obtained in an isothermal reversible expansion of an ideal gas:

 

 

Wm = 2.303 nRT log10

V2

V1

 

Wm = 2.303 nRT log10

P2

P1

 



 

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