• 12.1 Compare and contrast the mole as a number and the mole as a mass
• 12.1 Relate counting particles weighing samples of substances
• 12.1 Solve stoichiometry problems using mass

• 12.2 Predict quantities of reactants and products in chemical reactions.
• 12.2 Determine mole ratios from formulas for compounds
• 12.2 Identify formulas of compounds using mass ratios
• 12.2 Calculate percent yield

• A method of determining how much can be made
– In the business world, the question would be something like this: How many hamburgers can I make if I have 58 hamburger patties, 63 Buns, 120 pickle slices, and 32 ounces of Ketchup
– It takes 1 hamburger patty, 2 buns, 4 pickle slices, and 1 ounce of ketchup to make a burger

• 4NH
3
+ 5O
2

6H
2
O + 4NO
• How many grams of water can be made from 17grams of Ammonia and 32grams of
Water?
– Looks much more confusing than our real life example, but is the same

2 Buns + 1 Patty + 1 Cheese + 3 Pickles
 1 Hamburger
– 2 Buns
– 1 Beef Patty
– 1 Slice of Cheese
– 3 Pickle Slices
• 50 Buns, 30 Beef Patties, 22 Slices of Cheese,
64 Pickles
• 45 Buns, 16 Beef Patties, 31 Slices of Cheese,
48 Pickles

• To make an extremely tasty Vanilla Sundae, it takes the following materials
– 1 Plastic Cup
– 3 Scoops of Ice Cream
– 2 oz of Caramel
– 2 oz of Hot Fudge
• How many tasty Vanilla sundaes can be made from the following

1 Cup + 3 Scoops + 2 oz Caramel + 2 oz
Hot Fudge  1 Sundae
– 1 Plastic Cup
– 3 Scoops of Ice Cream
– 2 oz of Caramel
– 2 oz of Hot Fudge
• 15 Cups, 42 Scoops of Ice Cream, 24 oz of
Caramel, 32 oz of Hot Fudge
• 19 Cups, 62 Scoops of Ice Cream, 46 oz of
Caramel, 53 oz of Hot Fudge

– Can’t count individual atoms
• Count by mass
– Done by most manufacturing places who don’t want to count individual pieces
– A penny weighs 2 grams, if you have 1200 grams of pennies, how many pennies do you have?
• Different elements/isotopes have different masses
– Mass determined by amount of protons/neutrons

• The periodic table gives you the average mass of atoms which make up that element.
• The atomic mass on the periodic table directly converts into the mass that we can measure
– If you have 10 grams of hydrogen and 10 grams of oxygen, you have more hydrogen atoms than oxygen atoms

• The mass on the periodic table is equivalent to a Mol of the atom
– A dozen = 12
• A mol is a counting unit: 6 x 10 23
– 12 grams of carbon has 6 x 10 23 atoms of carbon
• Is a unit, or haven’t you heard, containing 6 x
10 to the 23 rd . That’s a 6, with 23 zero’s at the end, much to big a number to comprehend

• Is the application of your knowledge from previous slides to actual chemistry
• Example: How many mols of Ammonia can be made from 5 mols of N
2 and 12 mols of H
2
?
• N
2
+ 3 H
2

2 NH
3
• 5 mols of N
2
 10 mols NH
3
• 12 mols of H
2
 8 mols of NH
3

• Limiting Reagent: The substance you run out of first
– Hydrogen in previous example
• Excess Reagent: The substance you have more than enough of
– Nitrogen in previous example

• C
3
H
8
+ 5 O
2
 3 CO
2
+ 4 H
2
O
• A) How many mols of CO
2 from 3 mols of propane and 7 mols of Oxygen?
• B) How many mols of Propane and Oxygen are required to produce 9 mols of Water?

• 2 C
4
H
10
+ 13 O
2
---> 8 CO
2
+ 10 H
2
O, show what the following molar ratios should be.
– a. C
4 b. O
2
H
10
/ O
2
/ CO
2
O c. O
2 d. C
4 e. C
4
/ H
2
H
10
H
10
/ CO
/ H
2
2
O

• The mass of 1 mol of something is called the molar mass
– 1 mol of carbon is 12 grams (right off the table)
– 1 mol of water is 18 grams (2 mols of water and 1 mol of oxygen)
• What is the molar mass of Methane? Calcium
Chloride?



(
)

• In 6 grams of Carbon?
• In 36 grams of water?
• In 88 grams of Carbon Dioxide?
– 1 Mol = 6 x 10 23

• 1 mol of any gas takes up 22.4 L of space at
STP
• What is the density of Nitrogen gas at STP?
– Revisit Gas laws… PV =nRT
– We’ll pass on this for now, but if you really like chemistry, you’ll do stoichiometry with gases quite a bit in college.
– For example… following slide

Examples of Real Life Stoichiometry and Gases
• Air bags
– How much sodium azide needs to be placed into the bag?
• Car engines
– How much fuel should be placed into the piston?
(size of piston makes a difference)

N
2
(g) + 3H
2
(g)  2NH
3
(g)
• How many mols of hydrogen gas are required to make 68g of ammonia? Assume you have lots of nitrogen
• Will have another powerpoint dedicated to solving step by step these type of problems

• In a chemical reaction, you don’t always get the amount of what you expected
– Sometimes you make some products which you didn’t desire but end up with. For example, a pure combustion engine would produce only carbon dioxide and water. However, in real life, some carbon monoxide is made, as well as nitrogen oxides as well

• % Yield = Actual Yield / Theoretical Yield
– It is like your grade. 100% is possible, how much do YOU actually attain is your percent yield
• A certain reaction is supposed to produce 15 grams of ammonia but only 12 grams of ammonia are obtained. What is the % yield of the chemical reaction?

• How much of a substance by mass is a certain element?
• Water has a mass of 18grams. 2grams are hydrogen and 16g are oxygen. The mass % of water by element is
– Oxygen = 16g O / 18 g total = 89%
– Hydrogen = 2 g H / 18 g total = 11%
• Sugar is what % carbon?

• A certain chemical has a molar mass of 282 g.
It is composed of 76.5% C, 12.1 % H, and 11.3
% O. What is the chemical formula of Oleic
Acid?
• 282 g x 0.765 = 215.73 grams Carbon
• 215.73 g Carbon / 12 g = 18 mols Carbon

Mass Percents and Chemical Formulas
• 282 g x 0.121 = 34 .1 grams of Hydrogen
• 34.1g H / 1 g = 34 mols H
• 282 g x 0.113 = 31.8 grams of Oxygen
• 31.8 g / 16 g = 2 mols O
• Formula C
18
H
34
O
2

• Can be determined by knowing the ratio between the atoms and the molar mass of the atoms
• Done using mass percentages as well
• Empirical Formula = Lowest whole number ratio between atoms
– Ethane Molecular = C
2
H
6
– Empirical Ethane = CH
3

• Empirical of the below
– C
6
H
12
O
6
– C
2
O
4
• Molecular Formula
– Empirical NH
2
Molar mass 32g
– Empirical CO Molar mass 56g