When 2.246 grams of a calcium chloride hydrate was heated, 0.728 grams of water were

released. Determine the formula of the hydrate (Hint: take the same approach as for the

copper (II) sulfate hydrate).

CaCl₂.3H₂O

Explanation:

We are given;

Mass of calcium chloride hydrate as 2.246 grams Mass of water of Crystallization as 0.728 grams

We are supposed to determine the formula of the hydrate;

We are going to use the following steps. Step 1: Determine the number of anhydrous salt

Mass of anhydrous salt = Mass of the hydrate - mass of the water of crystallization

Mass of anhydrous CaCl₂ = 2.246 g - 0.728 g

= 1.518 g

Step 2: Calculate the number of moles of Anhydrous salt and water of crystallization.

Moles = Mass : Molar mass

Moles of anhydrous salt

Molar mass of anhydrous CaCl₂ = 110.98 g/mol

Moles of CaCl₂ = 1.518 g : 110.98 g/mol

= 0.0137 moles

Moles of water

Molar mass of water = 18.02 g/mol

Moles of water = 0.728 g : 18.02 g/mol

= 0.0404 moles

Step 3: Calculate the simplest whole number ratio of anhydrous salt to water.

CaCl₂ : H₂O

0.0137 moles : 0.0404 moles

0.0137/0.0137 : 0.0404/0.0137

1 : 2.94

1 : 3

We get; CaCl₂.3H₂O

Therefore; the formula of the hydrate is CaCl₂.3H₂O