PbCl2 [Lead(II) chloride] is sparingly soluble in water, meaning it has limited solubility. 1 At room temperature, only a small amount of PbCl2 will dissolve in water, forming a clear solution.
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Key Takeaways: Is PbCl2 Soluble in Water?
- PbCl2 has limited solubility in water due to its low solubility product constant (Ksp) and the stable crystal lattice structure.
- The relatively large lattice energy and less favorable hydration of Pb2+ ions contribute to its sparing solubility in water.
- PbCl2 is generally insoluble in most solvents except for water, with limited solubility in polar solvents such as HCl and CH3COOH due to the presence of chloride ions. It does not dissolve in nonpolar solvents.
Why is PbCl2 [Lead(II) chloride] sparingly soluble in water?
Lead(II) chloride (PbCl2) is sparingly soluble in water due to its low solubility product constant (Ksp) and the nature of its crystal lattice structure. When an ionic compound like PbCl2 dissolves in water, it dissociates into its constituent ions (Pb2+ and Cl–) due to the polar nature of water molecules. 2
The solubility of an ionic compound depends on the balance between the attractive forces holding the ions together in the solid state and the interactions between the ions and water molecules in the solution. 3
In the case of PbCl2, the compound has a relatively large lattice energy, which is the energy required to separate the ions in the solid crystal lattice. This indicates strong attractive forces between the Pb2+ and Cl– ions in the solid.
On the other hand, when PbCl2 dissolves in water, the hydration of the Pb2+ and Cl– ions occurs. Hydration is the process by which water molecules surround and interact with the ions, stabilizing them in the solution.
However, the hydration of Pb2+ ions is not as favorable as the hydration of smaller, highly charged ions like Na+ or K+. 4 5 The larger size of the Pb2+ ion and its lower charge density make the hydration process less favorable, resulting in a lower solubility.
Additionally, the crystal lattice structure of PbCl2 plays a role in its limited solubility. PbCl2 forms a crystalline structure in which the Pb2+ ions are surrounded by Cl– ions, and the Cl– ions are surrounded by Pb2+ ions. 6 This arrangement leads to a relatively stable crystal lattice, making it more difficult for water molecules to insert themselves between the ions and break up the lattice structure.
Overall, the combination of the relatively large lattice energy, less favorable hydration of Pb2+ ions, and the stable crystal lattice structure contribute to the sparing solubility of PbCl2 in water.
Can PbCl2 dissolve in other solvents?
PbCl2 (lead(II) chloride) is generally insoluble in most solvents apart from water. It exhibits limited solubility in polar solvents like hydrochloric acid (HCl) and acetic acid, where the presence of chloride ions can enhance its solubility. 7 However, PbCl2 is not soluble in nonpolar solvents.
Lead(II) chloride has a low solubility product constant (Ksp) and a high lattice energy, making it sparingly soluble. Its solubility in water is limited due to the unfavorable hydration of Pb2+ ions compared to smaller, highly charged ions.
In polar solvents like HCl and CH3COOH, the chloride ions can help solvate the Pb2+ ions, improving their solubility. However, the solubility remains relatively low overall. PbCl2 does not dissolve in nonpolar solvents because of the lack of polar interactions to overcome the ionic forces in the crystal lattice.
Further reading
Why is Calcium Chloride (CaCl2) Soluble in Water?
Why is NH4Cl (Ammonium Chloride) Soluble in Water?
Why is AgNO3 (Silver Nitrate) Soluble in Water?
Is AgBr (Silver Bromide) Soluble in Water?
Why is KBr (Potassium Bromide) Soluble in Water?
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References
- P. (n.d.). Lead chloride. Lead Chloride | PbCl2 | CID 24459 – PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/24459
- Lyle, K. (n.d.). Solubility_Products. Solubility_Products. https://www.chem.purdue.edu/gchelp/howtosolveit/Equilibrium/Solubility_Products.htm
- Okstate.edu https://intro.chem.okstate.edu/1515F01/Lecture/Chapter13/Lec91201.html
- 11.4: Hydration of Ions. (2016, May 9). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_ChemPRIME_(Moore_et_al.)/11%3A_Reactions_in_Aqueous_Solutions/11.04%3A_Hydration_of_Ions
- Uoregon.edu https://pages.uoregon.edu/chendon/coffee_literature/2007%20J.%20Phys.%20Chem.%20B,%20Salt%20making%20structure%20in%20water.pdf
- Sass, R. L., Brackett, E. B., & Brackett, T. E. (1963, December). THE CRYSTAL STRUCTURE OF LEAD CHLORIDE. The Journal of Physical Chemistry, 67(12), 2863–2864. https://doi.org/10.1021/j100806a517
- Lead(II) chloride – Wikipedia. (n.d.). Lead(II) Chloride – Wikipedia. https://en.wikipedia.org/wiki/Lead(II)_chloride
