1. Molar Relationships

2. Dozen = 12 Names associated with an amount Pair = 2
Can you think of any more?????

3. The Mole….. The mole (mol) is the amount of a substance that
contains as many elementary entities as there
are atoms in exactly grams of 12C
1 mol = NA = x 1023
Avogadro’s number (NA)

4. What is the mass of one mole of:C Hg Cu Fe
3.2

5. Molar Mass The Mass of 1 mole (in grams)
Equal to the numerical value of the average atomic mass (get from periodic table)
1 mole of C atoms =
1 mole of Cu atoms =
1 mole of S atoms =
1mole of Hg atoms =
1 mole of Fe atoms =

6. Learning Check! = 79.9 g/mole 1 mole of Br atoms 1 mole of Sn atoms
Find the molar mass (usually we round to the tenths place)
= 79.9 g/mole
1 mole of Br atoms
1 mole of Sn atoms
= g/mole

7. molecular mass (amu) = molar mass (grams)
Molecular mass (or molecular weight) is the sum of
the atomic masses (in amu) in a molecule.
SO2 1S
32.07 amu 2O
+ 2 x amu
SO2
64.07 amu
For any molecule
molecular mass (amu) = molar mass (grams)
1 molecule SO2 = amu
1 mole SO2 = g SO2
Let’s try some more……………..
3.3

8. Molar Mass of Molecules and Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses
1 mole of CaCl2 = g/mol
1 mole Ca x 40.1 g/mol
+ 2 moles Cl x 35.5 g/mol = g/mol CaCl2
Practice with this one: mole of N2O4 =

9. Learning Check! Molar Mass of K2O = ? Grams/mole
B. Molar Mass of antacid Al(OH)3 = ? Grams/mole

10. Learning Check
Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

11. So, if one mole = the formula mass how do we calculate….
The mass of 05 mol of Calcium Carbonate
The mass of 2.25 mol of Sodium Chloride

12. How many moles are there in?
100 g of Magnesium Hydroxide ?
64 g of Oxygen ?

13. Converting to # of atoms or molecules
How many atoms are in 3.00 moles of Iron?
How many atoms are in 0.25 moles of Water?

14. Molar Mass The molar mass of a compound is found by adding
Together the molar masses of all of its elements, taking
Into account the number of moles of each element present.
Homework: pg 157 # 5-11

15. Factor-Label Method (also called… dimensional analysis)
Use fractions that include numbers and units to convert from one item to another.
All fractions must have a valued of “1”
Example problem: How many seconds are there in one year?

16. Types of Mole Conversion Problems:
Grams to Moles Moles to Grams
Example Problem:
How many Moles are in 58 g of NaHCO3?
How many grams are in 3.75 Moles of Water?

17. Moles Particles (atoms,ions,molecules)
How many atoms are in .75 moles of Oxygen Gas?
How many moles are in x 1025 molecules of Calcium Hydroxide?
How many hydroxide ions are there in 4.5 Moles of Calcium Hydroxide?

18. So… Percent Composition the percentage by mass of
each element in a compound
Percent =
_______
Part
Whole
x 100%
So…
Percent composition
of a compound or =
molecule
Mass of element in 1 mol
____________________
x 100%
Mass of 1 mol

19. Percent Composition Molar Mass of KMnO4 K = 1(39.1) = 39.1
Example: What is the percent composition of Potassium Permanganate (KMnO4)?
Molar Mass of KMnO4
K = 1(39.1) = 39.1
Mn = 1(54.9) = 54.9
O = 4(16.0) = 64.0
MM = 158 g

20. Percent Composition Molar Mass of KMnO4 = 158 g 39.1 g K % K x 100 =
Example: What is the percent composition of Potassium Permanganate (KMnO4)?
Molar Mass of KMnO4
= 158 g
39.1 g K
% K
x 100 =
24.7 %
158 g
54.9 g Mn
34.8 %
x 100 =
% Mn
158 g
K = 1(39.10) = 39.1
64.0 g O
x 100 =
40.5 %
Mn = 1(54.94) = 54.9
% O
158 g
O = 4(16.00) = 64.0
MM = 158

21. Percent Composition
Determine the percentage composition of sodium carbonate (Na2CO3)?
Molar Mass
Percent Composition
46.0 g
x 100% =
43.4 %
Na = 2(23.00) = 46.0
C = 1(12.01) = 12.0
O = 3(16.00) = 48.0
MM= g
% Na =
106 g
12.0 g
x 100% =
11.3 %
% C =
106 g
48.0 g
x 100% =
45.3 %
% O =
106 g

22. Hydrates
Hydrated salt – salt that has water molecules trapped within the crystal lattice
Examples: CuSO4•5H2O , CuCl2•2H2O
Anhydrous salt – salt without water molecules
Examples: CuCl2
Can calculate the percentage of water in a hydrated salt.

23. Hydrated Compounds: Chemicals that usually have water associated with them.
How they are written:
BaCl2. 2H2O – Barium Chloride dihydrate
CuSO4.5H2O – Copper Sulfate pentahydrate
NaCO3.10H2O-__________________

24. Percent Composition
If 145 grams of copper (II) sulfate pentahydrate is completely dehydrated, how many grams of anhydrous copper sulfate will remain?
CuSO4 . 5 H2O
1. Molar Mass
2. % CuSO4
Cu = 1 x = g
S = 1 x = g
O = 4 x = g
MM = g
159.6 g
X 100 =
63.92 %
249.7 g
3. Grams anhydrous CuSO4
H = 2 x = 2.02 g
O = 1 x = g
MM = g
x 145 =
92.7 g
Mass of 5 moles of H2O =
5 x g = 90.1 g
Total Molar mass =
159.6 g g = g

25. Calculate the Molar Mass of Hydrates--
ZnSO4.7H2O
Na2CO3.10H2O

26. Formulas
Percent composition allow you to calculate the simplest ratio among the atoms found in compound.
Empirical Formula – formula of a compound that expresses lowest whole number ratio of atoms.
Molecular Formula – actual formula of a compound showing the number of atoms present
Examples:
C6H12O6
- molecular
C4H10
- molecular
C2H5
- empirical
CH2O
- empirical

27. Determining Empirical Formula
PERCENT
Grams in 100g sample
Moles
Mole Ratio
Empirical Formula C
40 %
40 g H
6.71%
6.71 g O
53.3%
53.3 g

28. Try this one: An oxide of aluminum is formed by the reaction of 4
Try this one: An oxide of aluminum is formed by the reaction of g of aluminum with 3.692g of oxygen. Calculate the empirical formula. E L
ments
PERCENT
Grams in 100g sample
Moles
Mole Ratio
Empirical Formula

29. A 4. 550 g sample of cobalt reacts with 5
A g sample of cobalt reacts with g chlorine to form a binary compound. Determine the empirical formula for this compound. E L
ments
PERCENT
Grams in 100g sample
Moles
Mole Ratio
Empirical Formula