Consider the spontaneous dissolution of NaCl in water: NaCl(s) → Na+(aq) + Cl −(aq) Predict whether the entropy change for this process is positive or negative and explain your answer. Then, predict whether the free energy change for the process is positive or negative and explain your answer.

Answer:

The entropy change (ΔS) for this process is positive. When a crystalline solid like NaCl dissolves, the ions move from a highly ordered solid lattice to a more disordered aqueous state, increasing randomness. The free energy change (ΔG) for this process is negative because it is described as a spontaneous process. For any process to be spontaneous at a given temperature and pressure, the change in Gibbs free energy must be less than zero (ΔG < 0).