Is CaSO4 Soluble in Water? (+ 2 Things to Know)

Calcium sulfate (CaSO4) has limited solubility in water. 1 It is considered sparingly soluble in water, meaning that only a small amount of CaSO4 can dissolve in water under normal conditions.

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Why is CaSO4 sparingly soluble in water?

CaSO4, or calcium sulfate, is sparingly soluble in water due to its ionic nature and the structure of its crystal lattice. When a substance is sparingly soluble in water, it means that only a small amount of the compound can dissolve in water to form a solution.

Here’s why CaSO4 is sparingly soluble in water:

  • Ionic nature: CaSO4 is an ionic compound composed of calcium ions (Ca2+) and sulfate ions (SO42-). 2 In the solid state, these ions are held together by strong ionic bonds. Water molecules are also polar and can interact with ions, but for CaSO4, the forces holding the ions together in the crystal lattice are stronger than the interactions between the ions and water molecules.
  • Lattice energy: The crystal lattice of CaSO4 is highly stable due to the strong electrostatic interactions between the calcium and sulfate ions. Breaking these ionic bonds requires energy, known as lattice energy. This energy is much higher than the energy released when the ions interact with water molecules during dissolution. As a result, the solid CaSO4 tends to remain intact rather than dissolving in water.
  • Ion-dipole interactions: When CaSO4 comes into contact with water, some ions at the surface of the crystal can interact with water molecules through ion-dipole interactions. 3 However, for the majority of the solid CaSO4, the internal ionic bonds prevent water molecules from penetrating the lattice and causing significant dissolution.

Overall, the combination of strong ionic bonding, high lattice energy, and limited ion-dipole interactions results in CaSO4 being sparingly soluble in water. As a consequence, only a small amount of CaSO4 will dissolve in water to create a dilute solution.

Further reading

Why is HCl (Hydrochloric Acid) Soluble in Water?
Is CCl4 Soluble in Water?
Is ZnS Soluble in Water?
Is ZnCl2 Soluble in Water?
Is AgI Soluble in Water?

About author

Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.

Read more about our Editorial process.


  1. Calcium sulfate – Wikipedia. (2008, January 10). Calcium Sulfate – Wikipedia.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top