Section 3.1 The Mole and Molar Mass

The Mole and Molar Mass

In this section…

a. Connecting the atomic and real worlds

b.The mole

c. Elemental molar mass

d.Compound molar mass

e.Conversions between atoms, moles, and mass

How do we relate atoms and molecules to the real world?

1 “mole” of atoms or molecules fills a small handful.

1 mole = 6.02 x 1023 atoms or molecules

1 mole of Cu, Al, S, K2Cr2O7, H2O and CuCl22H2O

1 mole = 6.02 x 1023 atoms or molecules

1 mole of elements Cu, Al, S,

1 mole = 6.02 x 1023 atoms or molecules

1 mole compounds K2Cr2O7, H2O and CuCl22H2O

The mole as a conversion factor

1 mol element = 6.02 x 1023 atoms of that element

The mole as a conversion factor

1 mol element = 6.02 x 1023 atoms of that element

moles atoms

atoms moles

1.95 mol Al

4.68 x 1023 Cu atoms

The mole as a conversion factor

1 mol element = 6.02 x 1023 atoms of that element

moles atoms

atoms moles

When doing these calculations,does it matter which elementis used?

Elemental molar masselemental molar mass = mass of 6.02 x 1023 atoms

elemental molar mass = atomic weight on periodic table, in grams per mole

Molar mass

1 mol Al =

1 mol F =

Molar mass as a conversion factor1 mol Al = molar mass Al = 26.98 g Al

moles grams

1.95 mol Al1.95 mol Al

Molar mass as a conversion factor1 mol Cu = molar mass Cu = 63.55 g Cu

grams moles

49.4 g Cu49.4 g Cu

Compound molar masscompound molar mass = mass of 6.02 x 1023 molecules

compound molar mass = sum of atomic weights of atoms in the molecule

SO2

Converting between grams and moles for a compound

Step 1. Determine molar massStep 2. Use molar mass as a conversion factor

Molar mass as a conversion factor

moles grams

What is the mass of a 1.45 mol sample of SO2?

grams moles

What amount, in moles, of SO2 does a 212-g sample represent?

SO2 = 64.06 g/mol

Multistep ProblemsHow many oxygen atoms are present in a 212-g sample of SO2?

Problem Map: