Hydrates

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Hydrates

Hydrates are compounds that have a specific number of water molecules attached to them.

An anhydrous compound is one that has no water

A dehydrated compound is one that had water but the water was removed.

The formula for a hydrate consists of the formula for the ionic compound and the number of water molecules associated with one formula unit.

The name of a hydrate consists of the compound named followed by the word “hydrate” with a prefix indicating the number of water molecules associated with one mole of compound.

Examples of hydrates

CoCl2 6· H2O is called Cobalt (II) chloride hexahydrate

BaCl2 2· H2O is called barium chloride dihydrate

FePO4 · 4H2O is called Iron (III) phosphate

tetrahydrate

Anhydrous compounds are formed when hydrates are heated and the water of hydration is driven off.

Information for these is calculated just like any other compound. 1. What is the formula mass for

sodium carbonate decahydrate?

2 What is the percent of water in sodium carbonate decahydrate?

8

3. What is the formula of a hydrate that is 76.9% lanthanum(III)carbonate and 23.9% water?

Answer: