Unit 5: Atomic Mass and the Mole

You will be able to:

1. use the factor-label method for conversions and calculations.
   calculate the molar mass of a substance given its chemical formula.
   state Avogadro’s number 6.022·10^23
   state the mass of Avogadro’s number of atoms for any elements by referring to the periodic table.
   relate the moles of a substance to the number of particles.
   relate the mass of a substance to the number of particles.

2. calculate the percent composition of a compound given its chemical formula.
   calculate the empirical formula of a compound given its percent composition.
   calculate the empirical formula of a compound given experimental data for its synthesis.
   calculate the molecular formula of a compound given, or determine as above, its empirical formula and molar mass.

Readings:

1. 10.1  Avogadro's Number
   10.2  Conversions Between Moles and Atoms
   10.3  Molar Mass
   10.4  Conversions Between Moles and Mass
   10.5  Conversions Between Mass and Number of Particles

2. 10.10  Percent Composition
   10.11  Percent of Water in a Hydrate
   10.12  Determining Empirical Formulas
   10.13  Determining Molecular Formulas

Slides

Laboratory

Dehydration of Barium Chloride

Materials: unknown hydrate of BaCl2

• Mass a small beaker

• Add approximately 1 g of BaCl2 into the beaker. Record the mass.

• Heat in drying oven at 110 °C for 48 hours.

• Reweigh the beaker.

• Calculate the percent hydration of the sample.

Worksheets

Additional Resources

The historical context for the mole (not tested, but interesting).

For a little fun:

Percent Composition