Barium sulfate (BaSO4) is considered insoluble in water, meaning it has very limited solubility. 1 It has a low solubility product constant (Ksp), indicating that only a small amount of BaSO4 will dissolve in water to form a saturated solution.
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Key Takeaways: Is BaSO4 (Barium Sulfate) Soluble in Water?
- Barium sulfate (BaSO4) is insoluble in water due to its strong ionic bonding and the nature of its crystal structure.
- Barium sulfate can dissolve to a small extent in strong acids, such as hydrochloric acid (HCl) or sulfuric acid (H2SO4).
- Barium sulfate’s solubility can slightly increase in hot concentrated solutions of some alkali metal sulfates or ammonium sulfate.
Why is Barium Sulfate (BaSO4) insoluble in water?
Barium sulfate (BaSO4) is insoluble in water due to its strong ionic bonding and the nature of its crystal structure.
To understand this, let’s break it down:
BaSO4 is composed of two ions: the barium ion (Ba)2+ and the sulfate ion (SO4)2-. In a crystal lattice, the ions are held together by electrostatic forces of attraction between oppositely charged ions. 2
The sulfate ion is highly soluble in water because it forms strong ion-dipole interactions with water molecules. The oxygen atoms in the sulfate ion can form hydrogen bonds with water molecules, leading to the dissolution of many sulfates.
However, the barium ion is considerably larger than the sulfate ion and has a high charge density. 3 Due to its size and charge, the barium ion has a strong attraction for sulfate ions, and the crystal lattice of barium sulfate is formed.
The ionic bonding in barium sulfate is so strong that it surpasses the strength of the ion-dipole interactions between the ions and water molecules. As a result, the crystal lattice of barium sulfate remains intact when placed in water, and the compound does not dissolve appreciably.
In summary, the insolubility of barium sulfate in water is primarily due to the strong ionic bonds between barium and sulfate ions, which prevent the compound from dissociating and dissolving in water. 4
Can BaSO4 dissolve in other solvents?
Barium sulfate (BaSO4) is generally considered insoluble in most common solvents, including organic solvent such as ethanol. 5 The strong ionic bonds between the barium and sulfate ions make it difficult for the compound to dissolve in these solvents.
However, there are a few exceptions where barium sulfate can exhibit limited solubility in certain solvents under specific conditions.
For example:
- Strong acids: Barium sulfate can dissolve to a small extent in strong mineral acids, such as hydrochloric acid (HCl) or sulfuric acid (H2SO4). 6 The acid reacts with the sulfate ions, forming soluble barium chloride (BaCl2) or barium hydrogen sulfate (Ba(HSO4)2).
- Hot concentrated solutions: Barium sulfate’s solubility can slightly increase in hot concentrated solutions of some alkali metal sulfates or ammonium sulfate. 7 8 This is because the increased temperature and concentration can overcome the lattice energy of the crystal, allowing a small amount of the compound to dissolve.
It’s worth noting that even in these exceptional cases, the solubility of barium sulfate remains relatively low compared to many other compounds.
In general, barium sulfate is still considered highly insoluble in most solvents and is commonly used as a contrast agent in medical imaging precisely because of its insolubility and inertness in the body.
Further reading
Is CaCO3 (Calcium Carbonate) Soluble in Water?
Why is Calcium Soluble in Water?
Why is KNO3 (Potassium Nitrate) Soluble in Water?
Is PbCl2 Soluble in Water?
Why is Calcium Chloride (CaCl2) Soluble in Water?
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References
- P. (n.d.). Barium Sulfate. Barium Sulfate | BaSO4 | CID 24414 – PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/24414
- Osti.gov https://www.osti.gov/pages/servlets/purl/1346634
- Atomic radii of the elements (data page) – Wikipedia. (n.d.). Atomic Radii of the Elements (Data Page) – Wikipedia. https://en.wikipedia.org/wiki/Atomic_radii_of_the_elements_(data_page)
- Is BaSO_4 ionic or covelent? | Socratic. (2017, August 22). Socratic.org. https://socratic.org/questions/is-baso-4-ionic-or-covelent
- CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data : Lide, David R : Free Download, Borrow, and Streaming : Internet Archive. (n.d.). Internet Archive. https://archive.org/details/crchandbookofche81lide/page/4
- Trenner, N. R., & Taylor, H. A. (1931, May 1). The Solubility of Barium Sulphate in Sulphuric Acid. The Journal of Physical Chemistry, 35(5), 1336–1344. https://doi.org/10.1021/j150323a015
- Barium sulfate – Wikipedia. (2022, October 12). Barium Sulfate – Wikipedia. https://en.wikipedia.org/wiki/Barium_sulfate
- Ali, A. M., & Messaoud, H. (2019, January). Barium Sulphate Deposits. Energy Procedia, 157, 879–891. https://doi.org/10.1016/j.egypro.2018.11.254
