Formula of a Hydrate HYDRATE An ionic compound

Formula of a Hydrate

HYDRATE • An ionic compound that contains water molecules in its structure • The formula states how many mol of water molecules per one mol of ionic compound • Example: Cu. So 4 5 H 20 Copper(II) sulfate pentahydrate

ANHYDRATE • The substance that remains after the water is removed from a hydrate • Example: Cu. So 4 Anhydrous Copper(II) sulfate

Prefixes 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca

Steps to find formula 1. Find the mass of anhydrate and water 2. Convert mass of both anhydrate and water to moles, respectively 3. Find the mole ratio of water to anhydrate 4. Write the formula and name

Example i A calcium chloride hydrate has a mass of 4. 72 g. After heated for several minutes the mass of the anhydrate is found to be 3. 56 g. Determine the formula and name of the hydrate. Calcium chloride: Ca 2+ Cl− Step 2: 4. 72 g hydrate − 3. 56 g anhydrate Ca. Cl 2 1. 16 g H 2 O Step 3: 3. 56 g Ca. Cl 2 1 mol Ca. Cl 2 = 0. 0321 mol. Ca. Cl 2 110. 98 g Ca. Cl 2 1. 16 g H 2 O 1 mol H 2 O = 0. 0644 mol H 2 O 18. 02 g H 2 O SIG FIGS IN ANSWER MUST MATCH GIVEN!!

Step 4: Ratio 0. 0644 mol H 2 O 0. 0321 mol Ca. Cl 2 ≈ 2 1 Step 5: Ca. Cl 2 2 H 2 O Step 6: calcium chloride dihydrate

Example ii A 15. 67 g sample of a hydrate of magnesium carbonate was heated, without decomposing the carbonate, to drive off the water. The mass of the anhydrate was found to be 7. 58 g. What is the formula and name of the hydrate?

Example iii What is the formula and name for a hydrate which consists of 76. 9% Ca. SO 3 and 23. 1% H 2 O?