For a spontaneous change ΔStotal must be positive.
During a chemical change: ΔStotal = ΔSsystem + ΔSsurroundings
In the ligand exchange reaction, where ‘en’ stands for ethylene diamine:
Co(NH3)63+ + 3en → Co(en)33+ + 6NH3
Discuss qualitatively the size and sign of the entropy change of the surroundings and the system, and comment on the stability of the ethylene diamine complex relative to the ammine. (4 marks)
A positive (+) entropy change means an increase in disorder. The universe tends toward increased entropy. All spontaneous change occurs with an increase in entropy of the universe. The sum of the entropy change for the system and the surrounding must be positive(+) for a spontaneous process.