1. 6.7 – NOTES Hydrates

2. 4. Hydrates
Definition: salt crystal with water molecules inside the crystal; if water is removed the substance becomes an anhydrous;
CuSO4  5 H2O + heat  CuSO H2O

3. CuSO H2O

4. Naming hydrates the salt is named as an ionic compound; the water is named with the word hydrate; a prefix is placed in front of hydrate to show how many water molecules are found inside the salt crystal;
1 = mono = di = tri = tetra 5 = penta
6 = hexa = hepta = octa = nona 10 = deca
For example – CuSO4  5H2O = copper II sulfate pentahydrate

5. Percentage composition of compounds (review of Chapter 3) and percentage composition of hydrates. Similar to finding % composition; when adding up the elements add up water as H2O;
Example:
Determine the percentage composition of sodium oxide.
Na2O
Na = 2 x 23.0 = % Na = 46.0 / 62.0 x 100 = 74.2%
O = 1 x = % O = 16.0 / 62.0 x 100 = 25.8%
62.0 g/ mol

6. Determine the percentage of water in Na2CO3 • 10 H2O.
Na = 2 x 23.0 = % H2O = 180. / 286 x 100 = 62.9%
C = 1 x = 12.0
O = 3 x = 48.0
106.0
H2O = 10 x 18.0 = 180.
286

7. Example: CuSO4 • 5H2O
Name the compound, then write the equation for the heating of this compound.
CuSO4 • 5 H2O = copper (II) sulfate (or cupric sulfate) pentahydrate
CuSO4 • 5 H2O  CuSO4 + 5 H2O (anhydrous + water)
water driven off as vapor

8. B. Determine the % of water in this compound.
Cu = x 100 = 36.1%
S =
O = (= 4x16.0)
H2O = 90.0 (= 5x18.0)
249.6