Hydrates

An ionic compound (i.e. a salt) that attracts
water molecules and forms loose chemical
bonds with them
 Anhydrous = “without water”

An anhydrous salt with water attached
 The compound has a specific number of water molecules
bounded to its atoms
 2 main parts: anhydrous solid (salt) and water
Copper (II) chloride dihydrate



Name the anhydrous solid first, then name
the water second
Usual naming rules apply for the anhydrous
solid
For the water add a prefix to the name
hydrate
 Prefix indicates how many water molecules are
present

The number of water molecules associated
with each formula unit of the compounds is
written following a dot – for example:
Na2CO3•5H2O (sodium carbonate
pentahydrate)
▪ A pentahydrate has 5 water molecules associated with
one formula unit of the compound.

To write formula: use criss cross method
learned with ionic compounds and use prefix
as the # of water molecules present

Name the following hydrates:
 CaCl2 ● 8 H2O
 FeSO4 ● 6 H2O
 LiOH ● H2O
 PbCl2 ● 3 H2O
 Li2CrO4 ● 5 H2O
 Na2SO4 ● 10 H2O

Write the formulas for the following hydrates:
 Barium Phosphate dihydrate
 Copper(II)sulfate pentahydrate
 Cobalt chloride hexahydrate
 Magnesium sulfate heptahydrate
 Nickel (II) sulfate hexahydrate
 Copper (I) Bromide tetrahydrate