Question

Question #eb1dc

Answer 1

Divide the mass of hydrated water (moles or mass, depending on the intent) by the mass of the entire compound.

Explanation:

A hydrated compound is usually indicated by a numerical prefix (Greek) in the name, or the written number in the formula. Hydrates are complete water molecules associated with a salt, so they are always indicated as a unit in the formula.

For example, copper (II) sulfate pentahydrate is the copper sulfate molecule with five (penta) water molecules. The formula is

`CuSO_4 o 5(H_2O)`. The mole ratio of water to the entire molecule is 5 moles `H_2O`/1 mole `CuSO_4`. The mass ratio is 90g/159.5g or 0.564 (56.4%). The amount of water in the entire molecule is 90/249.5 = 0.36 or 36%.