Naming hydrates

A crystalline compound that contains chemically bound water molecules in definite proportions is called a hydrate. Greek prefixes are used to indicate the number of water molecules in the formula unit.

Rules for naming hydrates:

1. Name the anhydrous salt. Again, determine whether the metal in the anhydrous salt is one that is fixed ionic charge or variable charge.
2. Name the metal, following the rules in naming for:
   • metal with fixed ionic charge, or
   • metal with variable charge
3. Name the chemically bound water molecules with the word hydrate with the appropriate Greek prefix to indicate the number of water molecules in the formula unit.

Example

CaSO₄· 2H₂O - calcium sulfate dihydrate

CoCl₂· 6H₂O - cobalt (II) chloride hexahydrate

Content suitability

BCIT courses: CHEM 0011