1. Chemical Formulas & Equations
Molar Mass
(Atomic Mass)

2. Molar Mass The molar mass:
Is the mass of one mole of an element or compound
Is the Atomic Mass expressed in grams (found on the periodic table!)
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

3. Molar (Atomic) Mass from Periodic Table
Molar mass is the atomic mass (AMU) expressed in grams…
This Mass is located below the Element Symbol on the periodic table
1 mole Ag mole C mole S
= g = g = g

4. Learning Check
Give the molar (atomic) mass for each (to the tenths decimal place)
A. 1 mole K atoms = ________
1 mole Sn atoms = ________
1 mole Pb atoms = ________

5. Formula Mass of a Compound
The formula mass of a compound is the sum (total) of the molar masses of all 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 x 2
71.0 g
CaCl2
111.1 g

6. Formula 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 P 1
31.0 g/mole O 4
16.0 g/mole
K3PO4

7. Formula Mass of a Compound Containing multiples of a Polyatomic
The formula mass of a compound is the total of the molar masses of all of the elements in the formula – and a Polyatomic in the formula – in parenthesis followed by a subscript - means the entire Polyatomic is multiplied by that number
Example: Calculate the molar mass of (NH4)2CO3
(NH4) is multiplied by 2!
2 Nitrogens…8 Hydrogens

8. Formula Mass of a Compound Containing multiples of a Polyatomic
Example: Calculate the molar mass of (NH4)2CO3
Element
Number of Moles
Atomic Mass
Total Mass N 2 H 8 C 1 O 3
(NH4)2CO3

9. Formula Mass of Mn3(PO4)4 Calculate the molar mass of Mn3(PO4)4.
Element
Number of Moles
Atomic Mass
Total Mass in Mn3(PO4)4 Mn P O
Mn3(PO4)4

10. Some One-mole Quantities
32.1 g g g g g

11. Learning Check
What is the molar mass of each of the following formulas? A. K2O B. Al(OH)3 C. (NH4)3PO4

12. Learning Check 1) 40.1 g/mole 2) 262 g/mole 3) 309 g/mole
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
1) g/mole
2) 262 g/mole
3) 309 g/mole