Which statement best explains why some metal salt solutions are acidic?

Which statement best explains why some metal salt solutions are acidic?

• A. Hydrolysis of the metal cation produces H+, making the solution acidic.
• B. Hydrolysis of the chloride anion produces OH-.
• C. The salt completely dissociates and leaves no effect on pH.
• D. Water autoionization dominates and sets pH to neutral.

Answer: (B)

The acidity of some metal salt solutions comes from hydrolysis of the metal cation. When a metal ion with a high charge density dissolves in water, it strongly interacts with nearby water molecules and pulls protons off them. This reaction produces hydronium ions (H3O+) in solution, lowering the pH and making the solution acidic. The more highly charged and smaller the metal ion, the stronger this effect tends to be. The anion, such as chloride from a strong acid, is a very weak base and does not significantly hydrolyze to produce hydroxide. That means it doesn’t counteract the acidity, so the overall solution remains acidic due to the metal cation’s hydrolysis. The idea that the chloride would hydrolyze to form OH− would imply basic behavior, which doesn’t explain the observed acidity.

The acidity of some metal salt solutions comes from hydrolysis of the metal cation. When a metal ion with a high charge density dissolves in water, it strongly interacts with nearby water molecules and pulls protons off them. This reaction produces hydronium ions (H3O+) in solution, lowering the pH and making the solution acidic. The more highly charged and smaller the metal ion, the stronger this effect tends to be.

The anion, such as chloride from a strong acid, is a very weak base and does not significantly hydrolyze to produce hydroxide. That means it doesn’t counteract the acidity, so the overall solution remains acidic due to the metal cation’s hydrolysis. The idea that the chloride would hydrolyze to form OH− would imply basic behavior, which doesn’t explain the observed acidity.