Stoichiometry

A. Proportional Relationships 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Makes 5 dozen cookies. I have 5 eggs. How many cookies can I make? Ratio of eggs to cookies 5 eggs 5 doz. 2 eggs = 12.5 dozen cookies

A. Proportional Relationships Stoichiometry mass relationships between substances in a chemical reaction based on the mole ratio Mole Ratio indicated by coefficients in a balanced equation 2 Mg + O2  2 MgO

B. Stoichiometry Steps 1. Write a balanced equation. Use Mole Island and Stoich Cheat Sheet B. Stoichiometry Steps 1. Write a balanced equation. 2. Identify the given and find. 3. Line up conversion factors. Mole ratio - moles  moles Molar mass - moles  grams Molarity - moles  liters soln Molar volume - moles  liters gas Mole ratio - moles  moles Core step in all stoichiometry problems!! 4. Check sig figs, units & circle your answer!

Conversion Factor # Moles A # Moles B The #’s in front of A & B MUST come from the balanced chemical equation

Mole – Mole Relationship Fe + O2  Fe2O3 1. Balance the reaction 2. Find the mole ratio of Iron to Oxygen 4 mol Fe / 3 mol O2 3. Find the mole ratio of Iron to Iron (III) oxide 4 mol Fe / 2 mol Fe2O3 4. Find the mole ratio it Oxygen to Iron (III) oxide 3mol O2 / 2 mol Fe2O3

Mole – Mole Relationship How many moles of Fe2O3 will form from 5.0 mols of Fe? 5.0 mole Fe x 2 mol Fe2O3 4 mol Fe 2.5 mol Fe2O3

Mole - Mole Relationship How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas? 2KClO3  2KCl + 3O2 ? mol 9 mol 9 mol O2 2 mol KClO3 3 mol O2 = 6 mol KClO3

Mole – Mass Relationship How many grams of NaCl will be produced from 1.25 mol of chlorine gas reacting with sodium? 1. What type of reaction is this? Write the balanced equation. 2 Na + Cl2  2NaCl

Mole – Mass Relationship 2. Work the problem. Remember Mole Ratio and Sigfigs! 1.25 mol Cl2 x 2 mol NaCl x 58.443 g NaCl 1 mol Cl2 1 mol NaCl 146 g NaCl

Mass to Mole Relationship Fe3O4 + 4 CO  3 Fe + 4 CO2 How many moles of CO are needed to react with 16.5 g of Fe3O4

Mass – Mass Relationships Ammonium nitrate decomposes into dinitrogen monoxide gas and water. Determine the amount of water produced if 25.0 g of ammonium nitrate decomposes. 1. Write the balanced reaction NH4NO3  N2O + 2 H2O

Mass – Mass Relationships 25.0 g NH4NO3 x 1 mol NH4NO3 x 2 mol H2O x 18.0153 g H2O 80.0434 g NH4NO3 1 mol NH4NO3 1 mol H2O 11.3 g H2O

Stoichiometry Problems How many grams of silver will be formed from 12.0 g copper? Cu + 2AgNO3  2Ag + Cu(NO3)2 12.0 g ? g 107.8662 g Ag 1 mol Ag 12.0 g Cu 1 mol Cu 63.546 g Cu 2 mol Ag 1 mol Cu = 40.7 g Ag