Stoichiometry

Baking 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?

Chemistry Recipes chemists have recipes as well, but we call them reaction equations we use moles to measure we use chemical compounds as our ingredients

Chemistry Recipes Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe) Be sure you have a balanced reaction before you start! Example: 2 Na + Cl 2  2 NaCl This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chloride

Guided Notes StoichiometryStoichiometry study of the quantity relationships in a chemical reactionstudy of the quantity relationships in a chemical reaction based on balanced chemical equationsbased on balanced chemical equations The coefficients in a balanced equation give the mole ratio for the substance involved in the reaction.The coefficients in a balanced equation give the mole ratio for the substance involved in the reaction.

Mole to Mole Conversions: 1.When elemental aluminum reacts with elemental iodine, aluminum iodide is produced. 2Al + 3I 2  2AlI 3 mole ratios: 2 mol Al = 3mol I 2 2 mol Al = 2 mol AlI 3 3 mol I 2 = 2 mol AlI 3 If you start with 4 moles of Al, how many moles of AlI 3 will be produced? 4 moles Al 2 mol AlI 3 2 mol Al = 4 moles AlI 3

2N 2 H 4 (g) + 1N 2 O 4 (g)  3N 2 (g) + 4H 2 O (g) a. How many moles N 2 O 4 is needed to react with 2.72 moles N 2 H 4 ? = moles N 2 O mol N2H4N2H b. How many moles of N 2 is produced from 2.72 moles N 2 H 4 ? = mole N mol N2H4N2H mol ? mol 2N 2 H 4 (g) + 1N 2 O 4 (g)  3N 2 (g) + 4H 2 O(g) 2.72 mol ? mol 2. Dinitrogen tetrahydride reacts with Dinitrogen tetroxide to produce nitrogen gas and water. Units match 2N 2 H 4 (g) + 1N 2 O 4 (g)  3N 2 (g) + 4H 2 O (g)

molar mass Avogadro’s number Grams Moles particles Everything must go through Moles!!! Calculations

Mass to Mole Conversions: 1. How many moles of water will be produced when 8.0 grams of hydrogen gas react with the oxygen in the air?1. How many moles of water will be produced when 8.0 grams of hydrogen gas react with the oxygen in the air? (Hint: To “make the switch” between different substances in a reaction, use the mole ratio from the balanced equation.)(Hint: To “make the switch” between different substances in a reaction, use the mole ratio from the balanced equation.) 2 H 2 + O 2  2 H 2 O 8.0 g H 2 1 mol H 2 2 mol H 2 O 2.0 g H 2 2 mol H 2 = 4.0 mol H 2 O

Mass to Mole Conversions: 2. In photosynthesis, carbon dioxide and water react to form glucose, C 6 H 12 O 6 and oxygen gas. 6 CO H 2 O  C 6 H 12 O O 2 If 15.6 grams of carbon dioxide react, how many moles of glucose will be producedIf 15.6 grams of carbon dioxide react, how many moles of glucose will be produced 15.6 g CO 2 1 mol CO 2 1 mol C 6 H 12 O g CO 2 6 mol CO 2 = mol C 6 H 12 O 6

Mass to Mole Conversions: 2. In photosynthesis, carbon dioxide and water react to form glucose, C 6 H 12 O 6 and oxygen gas. 6 CO H 2 O  C 6 H 12 O O 2 How many grams of carbon dioxide must react to produce 0.25 moles of glucose?How many grams of carbon dioxide must react to produce 0.25 moles of glucose? 0.25mol C 6 H 12 O 6 6 mol CO g CO molC 6 H 12 O 6 1 mol CO 2 = 66 g CO 2