Sulfate salts are soluble, except which of the following?

Sulfate salts are soluble, except which of the following?

• A. Barium Sulfate (BaSO4)
• B. Sodium Sulfate (Na2SO4)
• C. Magnesium Sulfate (MgSO4)
• D. Potassium Sulfate (K2SO4)

Answer: (A)

Solubility in water depends on the balance between lattice energy and hydration energy. Most sulfate salts dissolve because water can pull the ions apart and hydrate them. Barium sulfate is the exception because the forces holding Ba2+ and SO4^2− together in the solid are very strong, giving a high lattice energy. Water can’t overcome that energy well enough, so BaSO4 stays largely undissolved. The other sulfates—sodium sulfate, magnesium sulfate, and potassium sulfate—have lower lattice energies or are easier for water to hydrate, so they dissolve readily.

Solubility in water depends on the balance between lattice energy and hydration energy. Most sulfate salts dissolve because water can pull the ions apart and hydrate them. Barium sulfate is the exception because the forces holding Ba2+ and SO4^2− together in the solid are very strong, giving a high lattice energy. Water can’t overcome that energy well enough, so BaSO4 stays largely undissolved. The other sulfates—sodium sulfate, magnesium sulfate, and potassium sulfate—have lower lattice energies or are easier for water to hydrate, so they dissolve readily.