1. Molar Mass

2. Molar Mass The molar mass
is the mass of one mole of an element or compound.
Expressed in g/mol

3. Molar Mass from Periodic Table
1 mole Ag mole C mole S
= g = g = g

4. Molar Mass of an Element
To calculate molar mass use the atomic masses of all elements present in a compound
Molar Mass of CO2
= 1 x g/mol
44.01 g/mol
+ 2 x g/mol =

5. Molar Mass of a Compound
The molar mass of a compound is the sum of the molar masses of the elements in the formula.
Example: Calculate the molar mass of CaCl2.
Element
Number of Moles
Atomic Mass
Total Mass Ca 1
40.1 g/mole
40.1 g Cl 2
35.5 g/mole
71.0 g
CaCl2
111.1 g

6. Molar Mass of K3PO4 Calculate the molar mass of K3PO4. Element
Number of Moles
Atomic Mass
Total Mass in K3PO4 K 3
39.1 g/mole
117.3 g P 1
31.0 g/mole
31.0 g O 4
16.0 g/mole
64.0 g
K3PO4
212.3 g

7. Mole Conversion

8. Mole Map moles grams atoms Circle the numbers
Molar
Mass
atoms
6.02x1023
Circle the numbers
Underline what you are looking for
Start with what you circled
Check your answer with number of sig figs.

9. Mass to Mole Conversion
How many moles of carbon is
26 g of carbon?
26 g C
1 mol C
12.01 g C
= 2.2 mol C
Molar
Mass
moles
grams

10. How many moles is 5.69 g of Na? 5.69 g Na 1 mol Na 22.99 g Na moles
Molar
Mass
moles
grams 10

11. How many grams are in 9.45 mol of nitrogen atoms?
9.45 mol N
14.01 g N
1 mol N =
=132 g N
Molar
Mass
moles
grams 11 11

12. Remember… 1 Mole = 6.02 x 1023 atoms or molecules

13. Molar Conversion Examples
How many atoms are in 2.50 moles of C?
6.02  1023 atoms
1 mol
2.50 mol
1.51  1024
=atoms C
6.02x1023
atoms
moles

14. Calculate the number of atoms in 0.500 mol of Al.
3.01  1023
=atoms Al
6.02x1023
atoms
moles

15. Calculate the number of moles of 1.80 x 1024 Na atoms.
1.80 x 1024 atoms
= 2.99 moles
6.02x1023
atoms
moles

16. dinitrogen trioxide, N2O3 ?
How many grams are in
1.20 x1024 molecules of
dinitrogen trioxide, N2O3 ?
1.20  1024
molecules
1 mol
6.02  1023
molecules
76.02 g
1 mol
= g
=152 g N2O3
Molar
Mass
6.02x1023
atoms
moles
grams 16 16 16 16

17. Find the mass of 2.1  1024 molecules of NaHCO3. 2.1  1024 molecules
6.02  1023
molecules
84.01 g
1 mol
= 290 g NaHCO3
Molar
Mass
6.02x1023
atoms
moles
grams 17 17 17 17 17

18. Checking for understanding
1. How many atoms are in 5g of Ca?
2. How many atoms are in 1.2 mol K?
3. Calculate the mass of 1.4x molecules
of CaCO3

19. Click Below for the Video Lectures
The Mole

20. Percent Composition

21. Percent Composition by Mass
Part
X 100 %
Whole
The proportion by mass of the elements in a compound
Experimental Percent Composition
given mass of element in sample
X 100 %
given mass of total sample

22. Total = 80.0 g O = 56.0 g N = 24.0 g % O = (56.0g/80.0g) X 100 = 70.0%
A compound containing nitrogen and oxygen has a mass of 80.0 grams. Experiments show that the 80.0 grams is made up of 56.0 grams of oxygen and 24.0 grams of nitrogen. What is the % composition, by mass, of each element in the compound?
Total = 80.0 g
O = 56.0 g
N = 24.0 g
% O = (56.0g/80.0g) X 100 = 70.0%
%N = (24.0g/80.0g) X 100 = 30.0%

23. X 100 % Percent Composition
2) Determination by formula: You need the periodic table to do this.
mass of element in compound
X 100 %
mass of compound

24. What is the % composition, by mass, of each element in SiO2?
Molar mass of SiO2
= g + (2 x 16.00g ) = 60.1 g
%Si = (28.1g/60.1g) X 100 = 46.8%
%O = ( 32 g / 60.1 g) X 100 = 53.2%

25. Checking for understanding
Calculate the % composition, by mass, of each element in Al(OH)3