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**Stoichiometric Calculations (p. 275-287)**

Stoichiometry – Ch. 9 Stoichiometric Calculations (p )

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**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

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**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

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**B. Stoichiometry Steps 1. Write a balanced equation.**

2. Identify known & unknown. 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 answer.

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**Standard Temperature & Pressure**

C. Molar Volume at STP 1 mol of a gas=22.4 L at STP Standard Temperature & Pressure 0°C and 1 atm

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**C. Molar Volume at STP LITERS OF GAS AT STP Molar Volume MASS IN GRAMS**

(22.4 L/mol) MASS IN GRAMS MOLES NUMBER OF PARTICLES Molar Mass (g/mol) 6.02 1023 particles/mol Molarity (mol/L) LITERS OF SOLUTION

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**D. Stoichiometry Problems**

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

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**D. Stoichiometry Problems**

How many grams of KClO3 are req’d to produce 9.00 L of O2 at STP? 2KClO3 2KCl + 3O2 ? g 9.00 L 9.00 L O2 1 mol O2 22.4 L 2 mol KClO3 3 mol O2 122.55 g KClO3 1 mol KClO3 = 32.8 g KClO3

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**D. Stoichiometry Problems**

How many grams of silver will be formed from 12.0 g copper reacting with silver nitrate? Cu + 2AgNO3 2Ag + Cu(NO3)2 12.0 g ? g 12.0 g Cu 1 mol Cu 63.55 g Cu 2 mol Ag 1 mol Cu 107.87 g Ag 1 mol Ag = 40.7 g Ag

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**D. Stoichiometry Problems**

How many grams of Cu are required to react with 1.5 L of 0.10M AgNO3? Cu + 2AgNO3 2Ag + Cu(NO3)2 ? g 1.5L 0.10M 1.5 L .10 mol AgNO3 1 L 1 mol Cu 2 mol AgNO3 63.55 g Cu 1 mol Cu = 4.8 g Cu

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**D. Stoichiometry Problems – Mole-Mole**

N2H4 + N2O4 N2 + H2O BE SURE TO BALANCE THE EQUATION FIRST!! ? moles N2O4 = 2.72 moles N2H4 2 3 4 2.72 mol ? mol 2.72 mol N2 H4 1 mol N2O4 2 mol N2 H4 = 1.36 mol N2O4

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**D. Stoichiometry Problems**

Work on Handout – “Mole-Mole Problems”

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**D. Stoichiometry Problems – Mole/Mass**

In photosynthesis, carbon dioxide and water react to form glucose, C6H12O6 and oxygen gas. ___CO2 + ___H2O ___C6H12O6 + ___O2 If 15.6 grams of carbon dioxide react, how many moles of glucose will be produced? How many grams of carbon dioxide must react to produce 0.25 moles of glucose? 6 6 6 15.6 g CO2 1 mol CO2 1 mol C2 H12O6 = mol C2H12O6 44.01 g CO2 6 mol CO2 0.25 mol C2 H12O6 6 mol CO2 44.01 g CO2 = 66 g CO2 1 mol C2 H12O6 1 mol CO2

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**D. Stoichiometry Problems**

Work on Handout – “Mole-Mass Problems”

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**D. Stoichiometry Problems – Mass/Mass**

Sodium metal reacts with oxygen gas to produce solid sodium oxide. How many grams of sodium must react to produce 42.0 grams of sodium oxide? 4Na + O2 2Na2O ? g 42.0 g 42.0 g Na2O 1 mol Na2O 22.99 g Na 4 mol Na = 22.99 g Na 16.98 g Na2O 1 mol Na 2 mol Na2O

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**D. Stoichiometry Problems**

Work on Handout – “Mass-Mass Problems”

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