Post on 29-Jan-2016
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