Is ZnS Soluble in Water? (And Why?)

No, zinc sulfide (ZnS) is not soluble in water. 1 It is an insoluble compound in aqueous solutions due to its low solubility product (Ksp) value. The presence of strong electrostatic forces between the Zn2+ and S2- ions prevents significant dissolution in water.

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.

Key Takeaways: Is ZnS Soluble in Water?

  • Zinc sulfide (ZnS) is insoluble in water due to the strong electrostatic forces between its zinc and sulfide ions.
  • ZnS can dissolve to some extent in polar solvents with high dielectric constants, such as concentrated acids or alkalis.
  • The solubility of ZnS in solvents other than water is generally limited, and factors like pH, temperature, and concentration can affect its solubility.

Why is ZnS insoluble in water?

Zinc sulfide (ZnS) is generally considered insoluble in water because of its low solubility product. The solubility product is a measure of the equilibrium between the dissolved ions and the solid compound in a saturated solution. In the case of ZnS, the equilibrium is shifted towards the solid state, resulting in limited dissolution in water.

The solubility of ZnS in water is around 6.5 – 6.9 mg/L. 2 The low solubility of ZnS can be explained by the ionic nature of the compound and the interactions between the zinc and sulfide ions. ZnS consists of zinc cations (Zn2+) and sulfide anions (S2-). When ZnS is placed in water, the water molecules surround the ions and can interact with them through a process called hydration.

However, the forces of attraction between the zinc and sulfide ions in the solid state are generally stronger than the forces of hydration in the aqueous solution. As a result, the solid ZnS tends to remain intact, and only a small fraction of the compound dissociates into ions in water.

This limited dissociation leads to a low concentration of zinc and sulfide ions in the solution, which is why ZnS is considered insoluble.

Can ZnS dissolve in other solvents?

Zinc sulfide (ZnS) is insoluble in many common solvents, including nonpolar solvents such as benzene, hexane, and diethyl ether. These solvents lack the ability to break the strong ionic bonds between the zinc and sulfide ions in ZnS. However, ZnS can dissolve to some extent in certain polar solvents, particularly those with high dielectric constants that can effectively solvate the ions. 

Examples of polar solvents in which ZnS can dissolve include concentrated acids like hydrochloric acid (HCl) and nitric acid (HNO3), as well as some alkalis like sodium hydroxide (NaOH) solutions. 3 4

In acidic solutions, the sulfide ions can react with hydrogen ions (H+) to form hydrogen sulfide gas (H2S), which can be released from the solution. This reaction effectively increases the solubility of ZnS.

It’s important to note that even in solvents where ZnS can dissolve to some extent, the solubility is still relatively low compared to other compounds. 5 The exact solubility of ZnS in different solvents can depend on factors such as temperature, 6 concentration, and the presence of other substances.

Further reading

Is ZnCl2 Soluble in Water?
Is AgI Soluble in Water?
Is Bronze Magnetic?
Why is Galvanized Steel Magnetic?
Is Tungsten Magnetic?

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  1. Zinc sulfide – Wikipedia. (2017, October 1). Zinc Sulfide – Wikipedia.
  2. Zinc sulfide – American Chemical Society. (2020, October 26). American Chemical Society. https:///molecule-of-the-week/archive/z/zinc-sulfide.html
  3. Zhang, J., Lin, Z., Lan, Y., Ren, G., Chen, D., Huang, F., & Hong, M. (2006, September 8). A Multistep Oriented Attachment Kinetics: Coarsening of ZnS Nanoparticle in Concentrated NaOH. Journal of the American Chemical Society, 128(39), 12981–12987.
  4. Sciencemadness Discussion Board – ZnS solubility – Powered by XMB 1.9.11. (n.d.). Sciencemadness Discussion Board – ZnS Solubility – Powered by XMB 1.9.11.
  5. The solubility of sphalerite (ZnS) in sulfidic solutions at 25°C and 1 atm pressure. (2003, March 31). The Solubility of Sphalerite (ZnS) in Sulfidic Solutions at 25°C and 1 Atm Pressure – ScienceDirect.
  6. Ellis, A. J. (1959, September 1). The solubility of zinc sulfide in water at high temperatures | Economic Geology | GeoScienceWorld. The Solubility of Zinc Sulfide in Water at High Temperatures | Economic Geology | GeoScienceWorld.

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