An ionic compound (a salt) that has a specific number of water molecules weakly bound within its crystal structure.
What is the general rule for naming a hydrate?
Name the ionic compound using the standard rules (Type I or Type II), then add a Greek prefix to indicate the number of water molecules, followed by the word 'hydrate'.
How are the water molecules represented in the chemical formula of a hydrate?
The formula of the ionic compound is written first, followed by a centered dot (\(\cdot\)), then the number of water molecules followed by \(H_2O\). Example: \(CuSO_4 \cdot 5H_2O\).
Name the compound \(CuSO_4 \cdot 5H_2O\).
Copper(II) sulfate pentahydrate. (Copper is \(Cu^{2+}\), sulfate is \(SO_4^{2-}\). 'Penta' for \(5\) water molecules.)
Name the compound \(MgCl_2 \cdot 6H_2O\).
Magnesium chloride hexahydrate.
Name the compound \(Na_2CO_3 \cdot 10H_2O\).
Sodium carbonate decahydrate. (Also known as washing soda.)
What is the chemical formula for calcium chloride dihydrate?
$$ CaCl_2 \cdot 2H_2O $$
What is the chemical formula for cobalt(II) chloride hexahydrate?
$$ CoCl_2 \cdot 6H_2O $$
What is the term for a hydrate from which the water has been removed, for example, by heating?
It is called an anhydrous compound. For example, \(CuSO_4\) is anhydrous copper(II) sulfate.
