Warmup 11/19/15

Tell me a story about something that can soak up water

Objective Tonight’s HomeworkTo learn how chemicals can absorb and hold water

pp 214: 65, 66pp 215: 67, 68, 69

Notes on HydratesSome chemicals have the ability to soak up and hold water.

The water bonds to the chemical structure of the crystal.

Notes on HydratesSome chemicals have the ability to soak up and hold water.

The water bonds to the chemical structure of the crystal.

We call chemicals that can do this hydrates.

Hydrates usually contain a specific ratio of water to chemical.

Notes on HydratesTo write a hydrate, we write the chemical name just like regular, but add a dot and the number of water afterwards.

Notes on HydratesTo write a hydrate, we write the chemical name just like regular, but add a dot and the number of water afterwards.

Example: This is 1 molecule of copper

CuSO4 • 5H2O sulfate with 5 waters attached to each molecule.

Notes on HydratesTo name hydrates, we say the name of the molecule, and add on the type of hydrate.

Molecules of water Name 1 monohydrate 2 dihydrate 3 trihydrate 4 tetrahydrate 5 pentahydrate 6 hexahydrate 7 heptahydrate 8 octahydrate 9 nonahydrate 10 decahydrate

Notes on HydratesTo calculate the number of the hydrate we do the following:

Notes on HydratesTo calculate the number of the hydrate we do the following:

- Calculate the mass of the compound with water.- Heat it up to drive off all the water. (We call this anhydrous)- Measure the mass again and find the difference.

Notes on HydratesTo calculate the number of the hydrate we do the following:

- Calculate the mass of the compound with water.- Heat it up to drive off all the water. (We call this anhydrous)- Measure the mass again and find the difference.

This difference is the mass of the water. Find the number of the moles of dry material and of the water to find the ratio.

Notes on HydratesExample:What is the formula for a hydrate that is 90.7% SrC2O4 and 9.30% H2O?

SrC2O4 = 175.62 amuH2O = 18.01 amu

Next, we treat this like percent composition.

90.7 g * 1 / 175.62 = 0.5163 mol SrC2O4

9.7 g * 1 / 18.01 mol = 0.5385 mol H2O

Just about the same number, so our ratio is 1:1So… SrC2O4 ● H2O

Practice on HydratesOpen your book to page 218 and practice problems 114 and 116.

Like usual, the answers will be up front on the desk.

Exit Question

Name the following hydrate: Mn(NO3)2 • 4H2O

a) Manganese (II) Nitrate tetrahydrateb) Magnesium (II) Nitrate tetrahydratec) Manganese (II) Nitrate quadrahydrated) Magnesium (II) Nitrate quadrahydratee) Manganese (II) Nitratef) Magnesium (II) Nitrate