Stoichiometry

A. Proportional Relationships I have 5 eggs. How many cookies can I make? 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Makes 5 dozen cookies. 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 5 eggs5 doz. 2 eggs = 12.5 dozen cookies Ratio of eggs to cookies

A. Proportional Relationships 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 + O 2  2 MgO

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 Core step in all stoichiometry problems!! Mole ratio - moles  moles 4. Check sig figs, units & circle your answer! Use Mole Island and Stoich Cheat Sheet

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

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

Mole – Mole Relationship How many moles of Fe 2 O 3 will form from 5.0 mols of Fe? 5.0 mole Fe x 2 mol Fe 2 O 3 4 mol Fe 2.5 mol Fe 2 O 3

Mole - Mole Relationship How many moles of KClO 3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O 2 2 mol KClO 3 3 mol O 2 = 6 mol KClO 3 2KClO 3  2KCl + 3O 2 ? mol9 mol

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 + Cl 2  2NaCl

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

Mass to Mole Relationship Fe 3 O CO  3 Fe + 4 CO 2 How many moles of CO are needed to react with 16.5 g of Fe 3 O 4

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 NH 4 NO 3  N 2 O + 2 H 2 O

Mass – Mass Relationships 25.0 g NH 4 NO 3 x 1 mol NH 4 NO 3 x 2 mol H 2 O x g H 2 O g NH 4 NO 3 1 mol NH 4 NO 3 1 mol H 2 O 11.3 g H 2 O

Stoichiometry Problems How many grams of silver will be formed from 12.0 g copper? 12.0 g Cu 1 mol Cu g Cu = 40.7 g Ag Cu + 2AgNO 3  2Ag + Cu(NO 3 ) 2 2 mol Ag 1 mol Cu g Ag 1 mol Ag 12.0 g? g