Molar (Formula) Mass

Where do we find the atomic mass?

For every 1 mol, there are 22.99g!

Molar Mass

Molar (Formula) Mass – mass of a molecule

Units: g/mol“grams per mol”

Example 1

Is the molecule ionic or covalent?

Name the molecule:

Molecule = NaCl

(metal and nonmetal)

No prefixes for ionic

Ionic

Sodium Chloride

Example 1

# A atoms in molecule x atomic mass of A

# B atoms in molecule x atomic mass of B

Add those numbers

Molecule = NaCl

Na

1

x

22.99 g/mol

1

58.4 g/mol

Cl

x 22.99 g/mol

+

=

35.45 g/mol35.45 g/mol

Example 2

Is the molecule ionic or covalent?

Write the formula:

Molecule = Dihydrogen Monoxide

(nonmetals)Covalent

H2O

Example 2

# A atoms in molecule x atomic mass of A

# B atoms in molecule x atomic mass of B

Add those numbers

Molecule = H2O

H 2

x

1.01 g/mol

1

18.o2 g/mol

O

x

2.02 g/mol +

=

16.00 g/mol16.00 g/mol

Example 3

Is the molecule ionic or covalent?

Name the molecule:

Molecule = (NH4)2O

(has a polyatomic ion)

Made up of ions: NH4+ and

O2-

Ionic

Ammonium Oxide

Example 3Molecule = (NH4)2O

N: 2 x 14 = 28H: 8 x 1 = 8O: 1 x 16 = 16(NH4)2O: 52 g/mol

Example 4

Is the molecule ionic or covalent?

Write the formula:

Molecule = Beryllium Hydroxide

(has a polyatomic ion)

Ionic

Be(OH)2

Made up of ions: Be2+ and OH-

Example 4Molecule: Be(OH)2

Be: 1 x 9.01 g/molO: 2 x 16 = 32 g/mol

Be(OH)2 = 43.03 g/mol

H: 2 x 1.01 = 2.02 g/mol

Group PracticeCheck your answers when done

Chemical Formula

Molar Mass

KF

Na3PO4

Al2(CO3)3

Ca(SCN)2

Iron (III) Oxide

Dicarbon Tetrafluroide

Lead (II) Chromate

Boron Sulfate

Practice by Yourself

In your notes, find the molar mass of:1. H2O2

2. NaNO3

3. H2S4. (NH4)2S5. Ca3(PO4)2

6. Mg(NO3)2

7. Lithium Nitride8. Trinitrogen Pentabromide9. Iron (III) Nitrate10.Ammonium Carbonate