Chemistry TYPES OF PROCESSES

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TYPES OF PROCESSES

Thermodynamic Process :

The change of thermodynamic state from one condition to another condition is called thermodynamic process.

(i) `text(Reversible and Irreversible process)` : A process which is carried out so slowly that the system and the surroundings are always in equilibrium during the process is known as a Reversible Process (quasi-static). If this condition does not hold good, the process is said to be, irreversible. In a reversible process the driving force is infinitesimally larger than the opposing force. A reversible process in very slow and takes infinite time. Where as an irreversible process completes in finite time.

`text(Note)` : This thermodynamic reversible process is different from the `text(reversible reactions)`. The term `text(Reversible reaction)` only indicates that the reaction proceeds in both the directions. A process which proceeds without any external help is called a spontaneous process. All the real process are irreversible process.

(ii) `text(Isothermal Process)` :

(a) A process in which temperature of the system does not change throughout the studies.
(b) `dT= 0`
(c) It can be achieved by using thermostatic process.

(iii) `text(Adiabatic Process)` :

(a) A process in which exchange of heat between system and surrounding does not take place.
(b) `q = 0`
(c) It can be achieved by insulating the system boundaries for heat transfer.

(iv) `text(Cyclic Process)` :

(a) A process in which initial state of system is same after a series of operation.
(b) For a cyclic process `DeltaE = 0` and `DeltaH = 0`

(v) `text(Isochoric Process)` :

(a) A process in which volume of the system remains constant throughout the process.
(b) For an Isochoric process `Delta V=0`

(vi) `text(Isobaric process)` :

(a) A process in which pressure of the system remains constant throughout the process.
(b) Means `DeltaP = 0`

(vii) `text(Equilibrium)` : It is defined as when there is no change in thermodynamic property (`P`, `V`, `T` etc.) of system with time.

The change of thermodynamic state from one condition to another condition is called thermodynamic process.

(i) `text(Reversible and Irreversible process)` : A process which is carried out so slowly that the system and the surroundings are always in equilibrium during the process is known as a Reversible Process (quasi-static). If this condition does not hold good, the process is said to be, irreversible. In a reversible process the driving force is infinitesimally larger than the opposing force. A reversible process in very slow and takes infinite time. Where as an irreversible process completes in finite time.

`text(Note)` : This thermodynamic reversible process is different from the `text(reversible reactions)`. The term `text(Reversible reaction)` only indicates that the reaction proceeds in both the directions. A process which proceeds without any external help is called a spontaneous process. All the real process are irreversible process.

(ii) `text(Isothermal Process)` :

(a) A process in which temperature of the system does not change throughout the studies.
(b) `dT= 0`
(c) It can be achieved by using thermostatic process.

(iii) `text(Adiabatic Process)` :

(a) A process in which exchange of heat between system and surrounding does not take place.
(b) `q = 0`
(c) It can be achieved by insulating the system boundaries for heat transfer.

(iv) `text(Cyclic Process)` :

(a) A process in which initial state of system is same after a series of operation.
(b) For a cyclic process `DeltaE = 0` and `DeltaH = 0`

(v) `text(Isochoric Process)` :

(a) A process in which volume of the system remains constant throughout the process.
(b) For an Isochoric process `Delta V=0`

(vi) `text(Isobaric process)` :

(a) A process in which pressure of the system remains constant throughout the process.
(b) Means `DeltaP = 0`

(vii) `text(Equilibrium)` : It is defined as when there is no change in thermodynamic property (`P`, `V`, `T` etc.) of system with time.

Types of Equilibrium :

System and surrounding equilibrium condition is considered in three broader terms :

(i) Thermal equilibrium: Equality of temperature between system and surrounding.
(ii) Mechanical equilibrium: Equality of pressure between system and surrounding.
(iii) Material equilibrium : No. of moles of every substance in a definite phase remains constant with respect to time. Attained in closed vessel.

(a) Physical or phase equilibrium : Only physical changes are involved.

e.g. `A(s) ⇋ A(l)`
`A(s)⇋A(g)`
`A(l)⇋A(g)`

(b) Chemical equilibrium: `N_2 (g)+ 3H_2(g) ⇋ 2NH_3 (g)`

`PCl_5 (g) ⇋ PCl_3 (g) + Cl_2(g)`

In thermodynamics to deal with energy change during interaction of system and surrounding understanding of work (`w`) heat (`Q`, `q`) and internal energy (`U`, `E`) is very important.

System and surrounding equilibrium condition is considered in three broader terms :

(i) Thermal equilibrium: Equality of temperature between system and surrounding.
(ii) Mechanical equilibrium: Equality of pressure between system and surrounding.
(iii) Material equilibrium : No. of moles of every substance in a definite phase remains constant with respect to time. Attained in closed vessel.

(a) Physical or phase equilibrium : Only physical changes are involved.

e.g. `A(s) ⇋ A(l)`
`A(s)⇋A(g)`
`A(l)⇋A(g)`

(b) Chemical equilibrium: `N_2 (g)+ 3H_2(g) ⇋ 2NH_3 (g)`

`PCl_5 (g) ⇋ PCl_3 (g) + Cl_2(g)`

In thermodynamics to deal with energy change during interaction of system and surrounding understanding of work (`w`) heat (`Q`, `q`) and internal energy (`U`, `E`) is very important.

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