Why is Calcium Chloride (CaCl2) Soluble in Water?

Yes, calcium chloride (CaCl₂) is soluble in water. ¹ CaCl₂ is soluble in water because it is an ionic compound, and water molecules can effectively surround and interact with the calcium ions (Ca²⁺) and chloride ions (Cl^–) through hydration, allowing for their dispersion throughout the solution.

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.

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Explanation: Why is calcium chloride (CaCl2) soluble in water?

Calcium chloride (CaCl₂) is soluble in water due to its ionic nature and the strong attractive forces between the ions in the compound and the water molecules. When calcium chloride is added to water, the compound dissociates into its constituent ions: calcium ions (Ca²⁺) and chloride ions (Cl^–). ²

Water is a polar molecule, meaning it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. ³ The positive end of the water molecule (hydrogen) is attracted to the negatively charged chloride ions, while the negative end (oxygen) is attracted to the positively charged calcium ions.

The strong electrostatic attraction between the ions and water molecules leads to the hydration of the ions. Water molecules surround each ion, forming a shell of water molecules (hydration shell) through a process called solvation or hydration. The hydration of the ions helps to stabilize them in the solution.

The process of solvation is highly exothermic, releasing a significant amount of heat. ⁴ This phenomenon is often observed when calcium chloride is dissolved in water, resulting in an increase in temperature.

The combination of the strong attractive forces between the ions and water molecules and the heat released during the solvation process makes calcium chloride highly soluble in water.

What factors affect the solubility of calcium chloride in water?

Several factors can affect the solubility of calcium chloride (CaCl₂) in water. These factors include:

• Temperature: The solubility of most solid solutes, including calcium chloride, generally increases with an increase in temperature. As the temperature rises, the kinetic energy of the water molecules increases, leading to more frequent and energetic collisions with the solid particles. ⁵ This helps to break the intermolecular forces holding the solid together and promotes dissolution.
• Pressure: Unlike gases, the solubility of solids, including calcium chloride, is not significantly influenced by changes in pressure. Therefore, pressure has minimal effect on the solubility of calcium chloride in water. ⁶
• Ionic Strength: The presence of other ions in the solution, known as the ionic strength, can affect the solubility of calcium chloride. ^{7 8} High ionic strength, resulting from the presence of other soluble salts or ions, can decrease the solubility of calcium chloride by introducing competition for hydration with the chloride ions.
• pH: The pH of the solution can influence the solubility of calcium chloride indirectly. Changes in pH can affect the solubility of other compounds present in the solution, such as carbonates or hydroxides. ⁹ Precipitation or formation of insoluble compounds can occur, affecting the overall solubility of calcium chloride.

It’s important to note that the solubility of calcium chloride is relatively high in water across a wide range of temperatures, making it highly soluble compared to many other salts.

Can calcium chloride dissolve in other solvents besides water?

Yes, calcium chloride (CaCl₂) can dissolve in other solvents besides water. However, the degree of solubility may vary depending on the specific solvent and the temperature.

Calcium chloride is a highly soluble compound, and it can dissolve in polar solvents due to its ionic nature. Solvents such as methanol, ethanol, acetone, and glycerol are known to dissolve calcium chloride to some extent. ^{10 11 12} These solvents have polar characteristics that can interact with the positive and negative ions of calcium chloride, allowing for solvation and dissolution.

It’s important to note that the solubility of calcium chloride in non-aqueous solvents is generally lower compared to its solubility in water. The solubility can also be influenced by factors such as temperature, the presence of other solutes, and the relative polarities of the solvent and calcium chloride. ¹³

Additionally, calcium chloride is hygroscopic, meaning it has the ability to absorb moisture from the air. ^{14 15 16} This property can affect its solubility in solvents other than water, as it may attract and react with atmospheric water vapor, forming hydrated calcium chloride compounds.

Overall, while water is the most common and efficient solvent for dissolving calcium chloride, it is possible to dissolve calcium chloride in other polar solvents, although the solubility may be comparatively lower.

Further reading

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?
Why is K2SO4 (Potassium Sulfate) Soluble in Water?

1. Vrana, L. M. (2001, August 17). Calcium Chloride. Kirk-Othmer Encyclopedia of Chemical Technology. https://doi.org/10.1002/0471238961.0301120318050904.a01.pub2
2. Chemistry, life, the universe and everything. (n.d.). Chemistry, Life, the Universe and Everything. https://virtuallaboratory.colorado.edu/CLUE-Chemistry/chapters/chapter6txt-4.html
3. Acs.org https://www.acs.org/content/dam/acsorg/education/k-8/inquiry-in-action/fifth-grade/g5-l1.2-bkgd.pdf
4. Austincc.edu https://www.austincc.edu/athurwac/index1411Chapter14Notes.htm
5. Solubility. (n.d.). Solubility. https://www.chem.fsu.edu/chemlab/chm1046course/solubility.html
6. 13.4: Effects of Temperature and Pressure on Solubility. (2013, November 24). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_General_Chemistry%3A_Principles_Patterns_and_Applications_(Averill)/13%3A_Solutions/13.04%3A_Effects_of_Temperature_and_Pressure_on_Solubility
7. Common-ion effect – Wikipedia. (n.d.). Common-ion Effect – Wikipedia. https://en.wikipedia.org/wiki/Common-ion_effect
8. Lyle, K. (n.d.). Solubility_Products. Solubility_Products. https://www.chem.purdue.edu/gchelp/howtosolveit/Equilibrium/Solubility_Products.htm
9. 16.4: The Effects of pH on Solubility. (2015, December 27). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Principles_of_Modern_Chemistry_(Oxtoby_et_al.)/Unit_4%3A_Equilibrium_in_Chemical_Reactions/16%3A_Solubility_and_Precipitation_Equilibria/16.4%3A_The_Effects_of_pH_on_Solubility
10. Igem.org https://static.igem.org/mediawiki/2014hs/d/df/CaCl2CIDEB.pdf
11. Calcium chloride – Wikipedia. (2020, May 1). Calcium Chloride – Wikipedia. https://en.wikipedia.org/wiki/Calcium_chloride
12. Calcium chloride. (n.d.). Calcium Chloride. https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/wp/c/Calcium_chloride.htm
13. Solubility and Factors Affecting Solubility. (2013, October 2). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Solubilty/Solubility_and_Factors_Affecting_Solubility
14. Wang, X., Yang, D., Zhang, M., Hu, Q., Gao, K., Zhou, J., & Yu, Z. Z. (2022, July 18). Super-Hygroscopic Calcium Chloride/Graphene Oxide/Poly(N-isopropylacrylamide) Gels for Spontaneous Harvesting of Atmospheric Water and Solar-Driven Water Release. ACS Applied Materials & Interfaces, 14(29), 33881–33891. https://doi.org/10.1021/acsami.2c08591
15. Copernicus.org https://acp.copernicus.org/articles/19/2115/2019/acp-19-2115-2019.pdf
16. Vainio, E., DeMartini, N., Hupa, L., Åmand, L. E., Richards, T., & Hupa, M. (2019, September 23). Hygroscopic Properties of Calcium Chloride and Its Role on Cold-End Corrosion in Biomass Combustion. Energy & Fuels, 33(11), 11913–11922. https://doi.org/10.1021/acs.energyfuels.9b02731