How do you write the formula for the following compounds: Barium chloride dihydrate and Sodium sulfite heptahydrate?

1 Answer
Jan 28, 2017

Answer:

#BaCl_2*2H_2O#, and #Na_2SO_3*7H_2O#

Explanation:

#"Hydrate"# refers to a #"water of crystallization"#. #"Sulfite"# refers to the #SO_3^(2-)# counterion. When these material crystallize from water as their metal salts, the salt picks up several water molecules that are included in the solid state structure, the crystal (hence #"a water of crystallization"#).

We generally write these as shown. If we dried the salt, we could potentially remove the volatile water molecules; this would be a non-trivial exercise, but most of the time, inorganic chemists, who tend to use non-aqueous solvents, would dry the salt before use.