State Functions - Practice Questions & MCQ

Path and state function 
It is the path along which a change of state occurs. It is a path of change of a system from one equilibrium state or another which is usually accompanied by a change in energy or mass. 

Types of Thermodynamic Process

1. Isothermal Process 

Here the temperature is kept constant during each step of the process. Example, 

$\Delta \mathrm{T}=0, \Delta \mathrm{E}=0$

• It is achieved by using a thermostatic control. 

• Heat can be absorbed or evolved here that is, can be exchanged with the surroundings.

            For example, Freezing, melting, evaporation, condensation.

2. Isobaric Process 

Here the pressure is kept constant $(\Delta \mathrm{P}=0)$ during each step of the process. 

For example, Expansion of gas in an open system.

• Vaporization and heating of water up to its boiling point occur at the same atmospheric pressure.

3. Isochoric Process 

Here volume is kept constant. $(\Delta \mathrm{V}=0)$ during each step of the process.

For example, the Heating of substance in a closed vessel (system) or non-expanding chamber. 

4. Adiabatic Process 

• Here no exchange of heat takes place between the system and the surroundings that is, (Q = 0)

• It is achieved by insulating the system or in closed insulated containers (thermos).

5. Cyclic Process 

• Here the System undergoes a series of changes but finally comes back to the initial state.

• $\Delta \mathrm{E}=0, \Delta \mathrm{H}=0$