The phenomenon whereby sodium trioxocarbonate (IV) decahydrate loses some of its water of crystallization on exposure to the atmosphere is known as?

The phenomenon described in the question is known as efflorescence. This occurs when a hydrated salt loses some of its water of crystallization when exposed to air. As a result, the salt becomes less hydrated and may even crumble into a powder. Sodium trioxocarbonate (IV) decahydrate is a salt that contains ten molecules of water of crystallization, and when it loses some of these molecules, it undergoes efflorescence. The other options, deliquescence, hygroscopy, and effervescence, refer to different phenomena. Deliquescence is when a substance absorbs moisture from the air and dissolves in it, forming a liquid solution. Hygroscopy is the ability of a substance to absorb moisture from the air without necessarily dissolving in it. Effervescence is the bubbling or fizzing caused by the release of gas from a chemical reaction.