1. Mathematics of Chemistry The Mole

2. Mole = a specific Quantity like 1 dozen = 12 22.4L of any gas
6.02x1023 molecules
GFM gram formula mass
H2O H x 1 = 2
O x 16 = 16
18g = 1 mole
**GFM is the mass of a 1mole sample of any substance.
**All base on C12 as the standard so……
H1 has a mass of 1 and = 1/12 of Carbon
Dalton
The atom is made up of identical particles throughout
Particles are indivisible
Atom is made up of mostly (+) charge
Solid Billiard ball model

3. Gas
Amount
Volume
Molecules
Mass H2
1 Mole O2
CO2

4. ÷ Doc’s Mole Bridge X Mass Volume Volume Mole Mass Molecule Molecule
GFM
GFM
Mass
Mass

5. What about atoms or particles?
Substance
Quantity
Volume
(L)
(L)(
Molecules
Mass
(grams)
Atoms Or
Particles Mg
1 Mole
xxx
6.02x1023
24g H2
22.4L 2g
1.02x1024
CO2
44g
1.86x1024
X 1
X 2
X 3

6. Mass to Mole and Mole to Mass

7. Volume to Mole and Mole to Volume

8. Volume to Mole and Mole to Volume

9. Determine percent composition
Mass of the part x 100 = % comp.
Whole
1. Determine the GFM
H2O H 2 x 1 = 2
O 1 x 16 = 16
18g
part x 100 =%
whole /18 x 100 = 11% for H
16/18 x 100 = 89% for O
100%

11. Determine the molecular (True) formula from
the empirical formula and molecular mass.
Empirical is NO2 and the molecular mass is 92g
1. Determine the empirical mass
NO2 N 1 x 14 = 14
O 2 x 16 = 32
46g
2. determine how many times this goes into the molecular mass = quantity Molec Mass = quantity
empirical mass
92/46 = 2
Molecular formula is N2O4

12. Determine Molecular (True) Formula from Empirical Formula.
The empirical formula of a compound is CH2. Its molecular mass is 70g/mole.
What is its molecular formula?
A compound is found to be 40.0% Carbon, 6.7% Hydrogen and 53.5% Oxygen.
Its molecular mass is 60. g/mole. What is its Molecular formula?

13. Steps Determine the Empirical Formula from percent composition.
1. Change percent to gram 75% C = .75g
25% H = .25 g
2. Go from gram to mole
C /12 = mole
H /1 = .25 mole
3. Determine mole ratio (divide each by the lowest)
.0625/.0625 = 1 C
.25/ = H
Empirical Formula is CH4

15. Percent Composition of a Hydrate
1. Same as a % comp problem
2. Hydrate is a crystal that contains water
CuSO H2O This says that 1 mole of Copper II Sulfate contains
5 moles of water
****Calculate the percent of Water in the Hydrate?
Steps H2O
1. Calculate the gfm Cu 65, S 32 and 4 Oxy (18) = 251
part x x 100 = 36%
Whole
2. Determine percent of water in Na2S . 9 H20?

16. Stoichiometry made Simple
Remember not to panic, just do ratios
Piece of cake