Vocabulary Anhydrous salt: an ionic compound (i.e., a salt) that attracts water molecules and forms loose chemical bonds with them.
"anhydrous" = "without water"
symbolized by MN (M = metal, N = nonmetal) Hydrate: an anhydrous salt with water attached
symbolized by MN ?H2O (where ? is a "nice" number)
examples: Na2CO3. 10 H2O
CuSO4. 5 H2O
USES: in a dessicator, to keep chemicals dry
as dessicants (in vitamin bottles, leather goods, electronics equipment)
Dessicant Hygroscopic absorbs moisture from its environment
some restaurants put dry rice in the salt shaker to absorb moisture so that the salt doesn't "cake" (stick together).
Unsaturated "not full" [(a snack) or (dry sponge)] Saturated "full" [(a meal) or (soaking wet sponge)] Supersaturated ""ate too much" [Thanksgiving dinner...unstable and may "lose" material at any time]
Finding the Formula of a Hydrate from Experimental Data
1. Find the # of g of MN and # of g of H2O
2. Convert g --> mol
3. Divide each "# of mol" by the SMALLEST "#of mol"
4. Use the ratio to find the hydrate's formula
Example 1: Given
mass of sample before heating = 4.38 g (hydrate = MN + H2O)
mass of sample after heating = 1.93 g (anhydrous salt = MN)
molar mass of anhydrous salt = 85 g