Ncert Exercises & Solutions

Match the following process with entropy change

Reaction	Entropy change
A. A liquid vaporizes	1. $∆ S = 0$
B. Reaction is non-spontaneous at all temperatures and $∆ H$ is positive	2. $∆ S = positive$
C. Reversible expansion of an ideal gas	3. $∆ S = negative$

Codes

Hint: Gas has high entropy than liquid

A. When a liquid vaporises, i.e., liquid-vapour, entropy increases i.e.,

∆ S =

positive

B. When

∆ H =

positive, i.e., energy factor opposes. The process is non-spontaneous at all temperatures if entropy also

opposes the process, i.e.,

∆ S =

negative

C. In the reversible expansion of an ideal gas, the system remains in equilibrium at every stage. Hence,

∆ S = 0