Calcium chloride (CaCl₂) readily dissolves in water, forming a solution. Its high solubility makes it useful in various applications.
How Calcium Chloride Dissolves
Calcium chloride is an ionic compound, meaning it consists of positively charged calcium ions (Ca²⁺) and negatively charged chloride ions (Cl⁻) held together in a crystal lattice. Water molecules, on the other hand, are polar. This polarity means each water molecule has a slightly positive end (near the hydrogen atoms) and a slightly negative end (near the oxygen atom), due to the uneven sharing of electrons.
When calcium chloride is added to water, the polar water molecules are attracted to these charged ions. The slightly negative oxygen ends of water molecules surround the positive calcium ions, while the slightly positive hydrogen ends surround the negative chloride ions. This attraction pulls the ions away from the solid crystal lattice, a process known as dissociation.
The dissolution of calcium chloride in water is an exothermic process, releasing heat and often increasing the water temperature. The energy released when water molecules form “hydration shells” around the separated ions exceeds the energy needed to break the solid’s ionic bonds.
Common Uses of Calcium Chloride
Calcium chloride is widely used as a de-icing agent on roads and sidewalks, particularly in cold climates. Its ability to dissolve and release heat helps melt ice and snow quickly, even at temperatures as low as -25°F (-32°C). It also lowers the freezing point of water, preventing refreezing.
Its hygroscopic nature, a strong tendency to absorb moisture, makes it an effective desiccant. Calcium chloride can absorb a significant amount of water, up to 300% of its own weight. This property is used in industrial moisture control and preventing dampness in homes.
In the food industry, calcium chloride serves multiple purposes, including as a firming agent and in cheese production. It helps maintain the texture and crispness of canned fruits and vegetables, preventing them from becoming mushy during processing and storage. In cheesemaking, it is added to milk to improve curd formation and enhance the action of rennet, leading to a firmer curd and better cheese yield.
Calcium chloride is also used in swimming pools to adjust water chemistry. It increases the calcium hardness level of the water, which helps prevent pool components from corroding or scaling. Maintaining calcium hardness within a recommended range, typically between 200-400 parts per million (ppm), contributes to overall pool health and extends the lifespan of pool equipment.