Molar Mass

Molar Mass A compound is a collection of

bonded together.• Ethanol, CH3CH2OH, is made up of :

carbon atoms, hydrogen atoms, and oxygen atom,

2

6

1

atoms

_________

Molar Mass of CH3CH2OH How many molecules of ethanol are in one

mole of ethanol?

How many atoms of carbon are in one mole of ethanol?

Of hydrogen?

Of oxygen?

_____________________________

2 x (6.02 x 1023) atoms C !!

6 x (6.02 x 1023) atoms H !!

1 x (6.02 x 1023) atoms O !!

6.02 x 1023 molecules EtOH

Molar Mass of CH3CH2OH

How many moles of carbon are in one mole of ethanol?

Of hydrogen?

Of oxygen?

_________________________2 moles of carbon!!

___________________________ 6 moles of hydrogen!!

1 mole of oxygen!!________________________

Molar Mass In general, in a chemical formula, the

number of atoms of an element in a molecule of a compound is the same as the number of moles of that element in a mole of the compound.

C6H12O6 Fe2O3

Now let’s relate mass to moles in a chemical formula.

Molar Mass of CH3CH2OH

How many grams in 1 mole of carbon?

12.01g In 1 mole of hydrogen?

1.008g In 1 mole of oxygen?

16.00g

Molar Mass of CH3CH2OH Now let’s calculate the molar mass of

ethanol: 2 moles C 12.01g C = 24.02 g

1 mole C

6 moles H 1.008g H = 6.05 g 1 mole H

1 moles O 16.00g O = 16.00 g 1 mole O 46.07g

Molar Mass of EtOH = 46.07g/mole

Molar Mass

“The Molar mass of a compound is

the sum of the atomic masses for

each element in the compound,

multiplied by the number of times the

element occurs in the compound”.

Molar Mass - Practice Calculate the molar mass of:

NaCl =

Al2O3 =

C6 H12O6 =

Na3PO4 =

23.01g Na/mol + 35.45g Cl/mol = 58.45 g/mole

2(26.98gAl/mol) + 3(16.00gO/mol) = 101.96 g/mole

6(12.01gC/mol) + 12(1.008gH/mol) + 6(16.00gO/mol) = 180.16 g/mole

3(23.01gC/mol) + (30.97gP/mol) + 4(16.00gO/mol) = 117.98 g/mole