# What are hydrates?

Jan 27, 2017

Usually the word refers to salts with water 'built into' their crystals.

#### Explanation:

Example : Sodium carbonate $N {a}_{2} C {O}_{3}$ forms a white powder. To form larger crystals, it builds in 10 molecules of water into its crystal grid, to give $N {a}_{2} C {O}_{3} \cdot 10 {H}_{2} O$. This is called the hydrate.

An important hydrate is copper sulfate., because the anhydridic form $C u S {O}_{4}$ is white, while the hydrate $C u S {O}_{4} \cdot 5 {H}_{2} O$ is blue. It is thus a reagent for water, because it picks up the water molecules quite easily.
Another one is calcium chloride $C a C {l}_{2}$, which will dry damp spaces in your home, forming $C a C {l}_{2} \cdot 2 {H}_{2} O$.

Note :
This has nothing to do with carbo hydrates. They are called this way, because the ratio of $H$ and $O$ in them is always $2 : 1$, just as in water, while no real water is present.