Why is sodium chloride solution neutral and zinc chloride acidic?

Answer 1

The chemistry of the zinc ion is far more complex than that of the sodium ion because zinc forms a coordination complex when dissolved in water. Generally water ligands attach themselves to the zinc ion as neutral species. One of the water ligands readily gives up a proton to form a hydroxide ligand, resulting in the solution being acidic. Sodium ions do not form complexes in aqueous solution and thus won't affect the pH because it acts as a spectator ion unlike zinc which readily participates in a reaction to form the metal complex.