Entropy - Practice Questions & MCQ

Entropy- Entropy is a measure of the disorder of the molecular motion of a system. I.e Greater is the disorder, greater is the entropy.

The change in entropy is given as

The relation  is called the mathematical form of the Second Law of Thermodynamics.

1. Entropy for solid and liquid-

i. When heat is given to a substance to change its state at a constant temperature.

Then  change in entropy is given as 

where positive sign refers to heat absorption and negative sign to heat evolution.

And  and T is in kelvin.

ii. When heat is given to a substance to raises its temperature from 

Then  change in entropy is given as 

where   c = specific heat capacity 

2. Entropy for an ideal gas  -

For n mole of an ideal gas, the equation is given as PV = nRT

I.Entropy change for ideal gas in terms of T & V

 From the first law of thermodynamics, we know that 

and 

using PV = nRT  

II.Entropy change for an ideal gas in terms of T & P

III.Entropy change for an ideal gas in terms of P & V