Name the hydrate BaCl2·2H2O(s). Spelling counts.
The Correct Answer and Explanation is:
The hydrate barium chloride dihydrate is the name of the compound with the chemical formula BaCl2·2H2O(s).
In naming hydrates, the first part of the name is the name of the anhydrous (water-free) compound, which in this case is barium chloride (BaCl2). The second part of the name indicates the number of water molecules associated with the compound, represented by a prefix followed by the word “hydrate.” The prefix corresponds to the number of water molecules and uses the Greek system of prefixes (e.g., di- for two, tri- for three, etc.).
In this case, the prefix di- means two, indicating that there are two water molecules associated with each formula unit of barium chloride. Hence, the full name is barium chloride dihydrate.
Explanation:
- Barium chloride (BaCl2) is an ionic compound that consists of barium ions (Ba²⁺) and chloride ions (Cl⁻).
- Water of crystallization refers to water molecules that are chemically bound within the structure of a crystal. These water molecules are integral to the crystalline form but are not chemically bonded to the barium or chloride ions.
- The number of water molecules is indicated by a prefix. In this case, two water molecules are present, hence the name “dihydrate.”
- Anhydrous barium chloride (BaCl2) is the form of the compound without water molecules. When it crystallizes in the presence of water, it forms barium chloride dihydrate (BaCl2·2H2O).
Hydrates like this one are common in nature and are often encountered in laboratory settings where salts crystallize in the presence of water. The water molecules in hydrates can typically be removed by heating, and the compound then becomes an anhydrous form.
