Hydrates: Naming and Formula writing
Honors Chemistry/Langellier
Name
Period 1
2
4
Date
Naming hydrates ("hydrated salts") is pretty simple. Probably the hardest thing about it is that it's one more
set of rules on top of those already given for naming/formula writing for ionic compounds, molecular
compounds, and acids.
The good news is that naming them combines skills we already know: Each hydrate is an ionic compound,
with a specific ratio of water molecules trapped within the crystal structure. We simply name the ionic
compound, then add prefixhydrate to show how many water molecules go with each formula unit of the
ionic compound. When we write the formula, we use a 'dot' to separate the ionic formula from the water.
Example 1: Nickel (II) sulfate hexahydrate The ionic part is Ni+2 and SO4-2 = NiSO4, hexa = 6, so:
NiSO46H2O
Example 2: MnCl24H2O  Manganese is "special" so find its charge here: 2 Cl-1 ions have a total of
-2 charge, so Mn must be +2 to give zero net charge. Mn+2 is either Manganese (II) or manganous:
Manganese (II) chloride tetrahydrate, or manganous chloride tetrahydrate
Remember: XH2O on a compound is a HYDRATE, HX is HYDROxxxIC ACID, and
ClO-1 is HYPOCHLORITE. The names are close enough to confuse them, so don't!
Mg(NO3)26H2O
lithium hydroxide monohydrate
Pb(C2H3O2)23H2O
Ferric nitrate nonahydrate
Cu(NO3)23H2O
Cobalt (II) nitrate hexahydrate
CaSO42H2O
Sodium tartrate dihydrate
(if tartrate is C4H4O6-2)
Hydrates: Naming and Formula writing
Honors Chemistry/Langellier
Name
Period 1
2
4
Date
Naming hydrates ("hydrated salts") is pretty simple. Probably the hardest thing about it is that it's one more
set of rules on top of those already given for naming/formula writing for ionic compounds, molecular
compounds, and acids.
The good news is that naming them combines skills we already know: Each hydrate is an ionic compound,
with a specific ratio of water molecules trapped within the crystal structure. We simply name the ionic
compound, then add prefixhydrate to show how many water molecules go with each formula unit of the
ionic compound. When we write the formula, we use a 'dot' to separate the ionic formula from the water.
Example 1: Nickel (II) sulfate hexahydrate The ionic part is Ni+2 and SO4-2 = NiSO4, hexa = 6, so:
NiSO46H2O
Example 2: MnCl24H2O  Manganese is "special" so find its charge here: 2 Cl-1 ions have a total of
-2 charge, so Mn must be +2 to give zero net charge. Mn+2 is either Manganese (II) or manganous:
Manganese (II) chloride tetrahydrate, or manganous chloride tetrahydrate
Remember: XH2O on a compound is a HYDRATE, HX is HYDROxxxIC ACID, and
ClO-1 is HYPOCHLORITE. The names are close enough to confuse them, so don't!
Mg(NO3)26H2O
magnesium nitrate hexahydrate
LiOHH2O
lithium hydroxide monohydrate
Pb(C2H3O2)23H2O
Lead (II) acetate trihydrate
OR Ferrous acetate trihydrate
Fe(NO3)39H2O
Ferric nitrate nonahydrate
Cu(NO3)23H2O
Copper (II) nitrate trihydrate
OR cupric nitrate trihydrate
Co(NO3)26H2O
Cobalt (II) nitrate hexahydrate
CaSO42H2O
calcium sulfate dehydrate
Na2C4H4O62H2O
Sodium tartrate dihydrate
(if tartrate is C4H4O6-2)