Which of the following is not a reversible process ?

A. Expansion of an ideal gas against constant pressure

B. Atmospheric pressure vaporisation of water at 100°C

C. Solution of NaCl in water at 50°C

D. None of these

Answer: Option C

Solution(By Examveda Team)

Since the entropy of mixing is positive we can say the mixing process or solution formation process is an irreversible process.