substances that include water into their formula

water is not actually part of the chemical substance and this is reflected in the way the formula is written

For every one CuSO4, there are five water molecules

The dot IS NOT a multiplication sign. Remember, this is chemistry, not math.

No, the substance is not wet, it appears dry.

There are some hydrates that have a wet appearance, but most appear perfectly dry to the eye and to the touch.

penta meaning five and hydrate meaning water

CuSO4 . 5 H2O

Suppose you heard "trihydrate." What would you write?

. 3 H2O

Suppose you heard "octahydrate." What would you write?

. 8 H2O

Name this substance: MgSO4 . 9 H2O

Magnesium sulfate nonahydrate

Write the formula for: barium chloride dihydrate

BaCl2 . 2 H2O

Keep water’s mass separate in calculation

CuSO4 . 5 H2O

Cu = 63.5 g S = 32.1 g O = 16.0 x 4 = 64.0 g H2O = 18.0 g x 5 = 90.0g

› Add them all together to get the molar mass Total = 249.6 g (MOLAR MASS)

Calculating the accepted value:

How much water did we have?› 90.0 grams H2O

What was the total molar mass?› 249.6 grams

90.0 g x 100 = 36.1% H2O

249.6 g

You begin an experiment with 15.0 grams of hydrate.

You place the hydrate in an evaporating dish and place the Bunsen burner below.

You weigh your resulting product, 13.2 grams of anhydrous salt (a compound with all the water removed).

Determine the experimental percent composition of water within the compound

15.0 grams – 13.2 grams = 1.8 grams of water that was evaporated (removed)

1.8 g x 100 = 12.0% H2O

15.0 g