Question

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

released. Determine the formula of the hydrate

Answer 1

CaCl₂. 3H₂O

Step-by-step explanation:

We are given;

• Mass of calcium chloride hydrate as 2.246 g
• Mass of water of crystallization as 0.728 g

We are required to determine the formula of the hydrate;

First; we determine the mass of the anhydrous salt

Mass of anhydrous Calcium chloride = Mass of hydrate - mass of water

= 2.246 g - 0.728 g

= 1.518 g

Second; determine the moles of anhydrous salt and water

Moles = mass ÷ molar mass

Moles of anhydrous salt

Molar mass of 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

Third; we determine the whole number mole ratio of anhydrous salt to water

CaCl₂ : H₂O

0.0137 moles : 0.0404 moles

0.0137/0.0137 : 0.0404/0.0137

1 : 2.95

1 : 3

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