How Does Calcium Chloride Remove Water Vapor?

Hygroscopic Properties

As noted above, calcium chloride has hygroscopic properties. This means that it can attract water molecules by both absorption and adsorption. Absorption represents the way in which a fluid is absorbed by another solid or liquid. On the other hand, adsorption represents the process by which a substance physically binds to another surface.

Deliquescence

Calcium chloride is also deliquescent. This means that it can pull in such large amounts of water from the surrounding environment that it actually dissolves in the absorbed water. A key point to understand is that calcium chloride is a liquid brine in its natural state. This is why it absorbs water so readily when it is in its solid state and resultantly gives off energy during this reaction.

Thermodynamically Favorable Reaction

When calcium chloride combines with water, a new product is formed. Additionally there is a release of excess energy or heat. This means that the reaction is exothermic. Exothermic reactions are thermodynamically also more favorable, which can explain the inherent nature of the salt to attract water molecules.