I. Stoichiometric

Calculations

I. Stoichiometric

Calculations

StoichiometryStoichiometry

Chocolate Chip Cookies!!Chocolate Chip Cookies!!Chocolate Chip Cookies!!Chocolate Chip Cookies!!1 cup butter

1/2 cup white sugar

1 cup packed brown sugar

1 teaspoon vanilla extract

2 eggs

2 1/2 cups all-purpose flour

1 teaspoon baking soda

1 teaspoon salt

2 cups semisweet chocolate chips

Makes 3 dozen

How many eggs are needed to make 3 dozen cookies?

How much butter is needed for the amount of chocolate chips used?

How many eggs would we need to make 9 dozen cookies?

How much brown sugar would I need if I had 1 ½ cups white sugar?

Cookies and Chemistry…Cookies and Chemistry…Huh!?!?Huh!?!?Cookies and Chemistry…Cookies and Chemistry…Huh!?!?Huh!?!? Just like chocolate chip

cookies have recipes, chemists have recipes as well

Instead of calling them recipes, we call them reaction equations

Furthermore, instead of using cups and teaspoons, we use moles

Lastly, instead of eggs, butter, sugar, etc. we use chemical compounds as ingredients

A. Proportional A. Proportional RelationshipsRelationshipsA. Proportional A. Proportional RelationshipsRelationships

I have 5 eggs. How many cookies can I make?

3/4 c. brown sugar1 tsp vanilla extract2 eggs2 c. chocolate chipsMakes 5 dozen cookies.

2 1/4 c. flour1 tsp. baking soda1 tsp. salt1 c. butter3/4 c. sugar

5 eggs 5 doz.

2 eggs= 12.5 dozen cookies

Ratio of eggs to cookies

A. Proportional A. Proportional RelationshipsRelationshipsA. Proportional A. Proportional RelationshipsRelationships

StoichiometryStoichiometry• mass relationships between

substances in a chemical reaction• based on the mole ratio

Mole RatioMole Ratio• indicated by coefficients in a

balanced equation

2 Mg + O2 Mg + O22 2 MgO 2 MgO

B. Stoichiometry StepsB. Stoichiometry StepsB. Stoichiometry StepsB. Stoichiometry Steps

1. Write a balanced equation.2. Identify known & unknown.3. Line up conversion factors.

• Mole ratio - moles moles• Molar mass - moles grams

Core step in all stoichiometry problems!!

• Mole ratio - moles moles

4. Check answer.

Amount of moles

2H2 + O2 2H2O

Means2 moles H2 + 1 mole O2 2 Moles

H2O

Amount of AtomsAmount of AtomsAmount of AtomsAmount of Atoms

2H2 + O2 2H2O

Means

4 atoms H + 2 atoms O

4 atoms H and 2 atoms O

Amount of Molecules

2H2 + O2 2H2O

Means2 molecule H2 + 1 molecule O2 2 Molecules H2O

Mass

2H2 + O2 2H2O

Means(2x2.02) g H2 + 32.00 g O2 (2x18.02) g H2O

RatiosRatiosRatiosRatios

2H2 + O2 2H2O

2 moles H2 2 moles H2

1 mole O2 2 moles H2O

1 mole O2 * FLIP FLOP THESE

2 moles H2O